user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: what is the name of the pittsburgh steelers head coach? 
Knowledge Triplets: Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, american_football.football_game.passing, m.0793j8b
Pittsburgh Steelers, common.topic.webpage, m.0422hz1
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.07926zd
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g386l
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl6_
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g382c
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, common.topic.notable_for, g.125689xm8
m.04xwl7h, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g387g
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.0792d6r
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0793q80
Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, american_football.football_game.passing, m.0792b2l
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rw6
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g3842
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.0792b0v
Pittsburgh Steelers, sports.professional_sports_team.owner_s, Rooney family
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl83
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbhg
Pittsburgh Steelers at Jacksonville Jaguars, 2008-10-05, american_football.football_game.receiving, m.0792bnc
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0793q6x
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.away_team, Pittsburgh Steelers
Pittsburgh Steelers, american_football.football_coach.current_team_head_coached, Mike Tomlin
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mljz8
Pittsburgh Steelers, american_football.football_team.conference, American Football Conference
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbrz
Pittsburgh Steelers, common.topic.article, m.05tfy
Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, american_football.football_game.receiving, m.0793jfg
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g3831
Pittsburgh Steelers at Jacksonville Jaguars, 2008-10-05, common.topic.notable_for, g.125h3jddn
Pittsburgh Steelers at Denver Broncos, 2009-11-09, common.topic.notable_for, g.12561994g
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, common.topic.notable_for, g.125ddf772
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901r8c
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl6c
Pittsburgh Steelers at New England Patriots, 2008-11-30, common.topic.notable_for, g.125g473dj
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48yg
Pittsburgh Steelers at Cincinnati Bengals, 2008-10-19, american_football.football_game.passing, m.0792br9
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.07922t3
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.passing, m.07929_b
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.passing, m.0901rct
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlk7h
m.0n7wv_d, sports.sports_team_coach_tenure.team, Pittsburgh Steelers
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.rushing, m.07mljyd
Pittsburgh Steelers, common.topic.webpage, m.09wbscp
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl7h
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48qy
m.09w8wnq, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.0792719
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.passing, m.0793q3j
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl7c
m.04xwl8h, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g3856
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.passing, m.0901rdg
Pittsburgh Steelers, sports.sports_team.coaches, m.0n7wv_d
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48rm
m.04xwl7c, american_football.football_historical_coach_position.team, Pittsburgh Steelers
m.04xwl6w, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g3819
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rrb
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbf3
Pittsburgh Steelers at Cincinnati Bengals, 2008-10-19, common.topic.notable_for, g.125btxq91
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbpj
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rc3
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.0792b1z
m.09wb9ch, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rvd
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlkcm
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mljzp
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g384w
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl6h
Pittsburgh Steelers, common.topic.webpage, m.09wbb6g
Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, american_football.football_game.receiving, m.0792b6f
m.04xwl7m, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.07926rt
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlk2x
Steely McBeam, sports.mascot.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g383r
m.04xwl8c, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers, common.topic.webpage, m.09wdwcx
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.07926x7
Pittsburgh Steelers, common.topic.webpage, m.09w949m
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48y3
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbdj
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.07926wf
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.0792b16
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlk0j
m.04xwl77, american_football.football_historical_coach_position.team, Pittsburgh Steelers
m.04xwl87, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers, sports.sports_team.team_mascot, Steely McBeam
Pittsburgh Steelers, american_football.football_team.current_head_coach, Mike Tomlin
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g381n
m.09w949m, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Jacksonville Jaguars, 2008-10-05, american_football.football_game.receiving, m.0792bnz
Pittsburgh Steelers, american_football.football_team.away_games, Pittsburgh Steelers at Cleveland Browns, 2008-09-14
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g387t
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.07922s5
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.rushing, m.096qbnk
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0792c5c
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.home_team, Cleveland Browns
m.09wdwcx, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48sm
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlkbq
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl7m
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g381_
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rw_
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbfx
Pittsburgh Steelers at Washington Redskins, 2008-11-03, common.topic.notable_for, g.1259m4sn3
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlkc8
m.09wbscp, common.webpage.topic, Pittsburgh Steelers
m.04xwl7r, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.07926v8
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.passing, m.09g384f
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.07926_4
m.0422hz1, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbr3
Pittsburgh Steelers, common.topic.webpage, m.09wb0f4
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.passing, m.07922mc
Pittsburgh Steelers, common.topic.webpage, m.0gw54r6
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl7_
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.07929_s
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901r3d
m.04xwl73, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlk15
Pittsburgh Steelers, common.topic.webpage, m.09w8wnq
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.07922rt
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, common.topic.notable_for, g.1259v06hn
Pittsburgh Steelers, common.topic.webpage, m.09xjydp
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl7r
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl73
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbgg
Pittsburgh Steelers, common.topic.notable_for, g.1258jnh_h
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.07926ym
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.passing, m.0792c0t
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.passing, m.07mljwd
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.0792705
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.passing, m.07t48tz
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0792c61
m.04xwl83, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, common.topic.notable_for, g.12558wqy_
Pittsburgh Steelers at Cincinnati Bengals, 2008-10-19, american_football.football_game.passing, m.07924rn
m.04xwl6r, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48xs
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.passing, m.096qbj1
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48tk
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlk6_
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.07926p8
Mike Tomlin, american_football.football_coach.current_team_head_coached, Pittsburgh Steelers
m.09wbs6z, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901r21
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901r5w
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901r6p
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rsm
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g383d
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl6m
Pittsburgh Steelers, common.topic.webpage, m.09wbs6z
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48r8
Pittsburgh Steelers, sports.sports_team.sport, American football
m.0gw54r6, common.webpage.topic, Pittsburgh Steelers
m.09xjydp, common.webpage.topic, Pittsburgh Steelers
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48yv
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.passing, m.0792d47
Pittsburgh Steelers, common.topic.webpage, m.0b461hx
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.0792b0h
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g385k
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.07922rf
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, common.topic.notable_for, g.1256knc1q
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.passing, m.0792c0c
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlk8y
Pittsburgh Steelers at Detroit Lions, 2009-10-11, common.topic.notable_for, g.1255c58_j
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.passing, m.07926mr
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl8h
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.0792d83
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901ryb
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g385x
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0793qb5
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.passing, m.07mlk3t
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl6w
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48ws
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0793q9b
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.season, 2008 NFL season
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.receiving, m.09g3867
Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, common.topic.notable_for, g.125h5bpg8
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl8c
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rtv
m.03z8bkq, business.employment_tenure.company, Pittsburgh Steelers
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.07926tg
m.04xwl7w, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48ql
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlkcz
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901r9s
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.passing, m.09g380w
Pittsburgh Steelers, common.topic.webpage, m.03nbxbp
m.04xwl7_, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48sz
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.passing, m.07t48my
Pittsburgh Pirates, sports.defunct_sports_team.later_known_as, Pittsburgh Steelers
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl7w
Pittsburgh Steelers at Washington Redskins, 2008-11-03, american_football.football_game.receiving, m.0792c6m
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbh0
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.0792d6d
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl87
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48pr
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl6r
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.passing, m.096qb7h
Pittsburgh Steelers, common.topic.webpage, m.09wb9ch
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.receiving, m.0901rpw
Pittsburgh Steelers, sports.sports_team.previously_known_as, Pittsburgh Pirates
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.receiving, m.0792b1l
m.04xwl6_, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Baltimore Ravens, 2009-11-29, american_football.football_game.receiving, m.096qbct
Pittsburgh Steelers, american_football.football_team.historical_coaching_staff, m.04xwl77
Pittsburgh Steelers at Kansas City Chiefs, 2009-11-22, american_football.football_game.passing, m.0901qyg
Pittsburgh Steelers at Baltimore Ravens, 2008-12-14, american_football.football_game.receiving, m.07922sk
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.0792b04
Pittsburgh Steelers at Cleveland Browns, 2009-12-10, american_football.football_game.rushing, m.09g382q
Pittsburgh Steelers at Detroit Lions, 2009-10-11, american_football.football_game.receiving, m.07t48xf
Pittsburgh Steelers, common.topic.notable_types, Professional Sports Team
m.04xwl6m, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Chicago Bears, 2009-09-20, american_football.football_game.receiving, m.07mlj_1
Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, american_football.football_game.passing, m.0792b30
m.04xwl6c, american_football.football_historical_coach_position.team, Pittsburgh Steelers
m.04xwl6h, american_football.football_historical_coach_position.team, Pittsburgh Steelers
Pittsburgh Steelers at Philadelphia Eagles, 2008-09-21, american_football.football_game.receiving, m.0792b9b
Pittsburgh Steelers, american_football.football_team.division, AFC North
Pittsburgh Steelers at Cleveland Browns, 2008-09-14, american_football.football_game.rushing, m.07926qy

Answer: Mike Tomlin