How many draft picks are there at the linebacker position?
{'header': ['Pick #', 'NFL Team', 'Player', 'Position', 'College'], 'page_title': '1984 Denver Broncos season', 'page_id': '', 'types': ['real', 'text', 'text', 'text', 'text'], 'id': '1-16729063-1', 'section_title': 'NFL Draft', 'caption': 'NFL Draft', 'rows': [['46', 'Denver Broncos', 'Andre Townsend', 'Defensive End', 'Mississippi'], ['78', 'Denver Broncos', 'Tony Lilly', 'Defensive Back', 'Florida'], ['89', 'Denver Broncos', 'Randy Robbins', 'Defensive Back', 'Arizona'], ['159', 'Denver Broncos', 'Aaron Smith', 'Linebacker', 'Utah State'], ['186', 'Denver Broncos', 'Clarence Kay', 'Tight end', 'Georgia'], ['207', 'Denver Broncos', 'Winford Hood', 'Tackle', 'Georgia'], ['218', 'Denver Broncos', 'Scott Garnett', 'Defensive tackle', 'Washington'], ['245', 'Denver Broncos', 'Chris Brewer', 'Running back', 'Arizona'], ['272', 'Denver Broncos', 'Bobby Micho', 'Tight end', 'Texas'], ['299', 'Denver Broncos', 'Gene Lang', 'Running back', 'Louisiana State']], 'name': 'table_16729063_1'}