What is the rank of london borough in southwark?
{'header': ['Rank', 'London Borough', 'Black African Population', 'Black Caribbean Population', 'Other Black Population', 'Total Black Population'], 'page_title': 'Ethnic groups in London', 'page_id': '', 'types': ['real', 'text', 'real', 'real', 'real', 'real'], 'id': '1-19149550-7', 'section_title': 'Black Population of London', 'caption': 'Black Population of London', 'rows': [['1', 'Lambeth', '35187', '28886', '14469', '78542'], ['2', 'Southwark', '47413', '17974', '12124', '77511'], ['3', 'Lewisham', '32025', '30854', '12063', '74942'], ['4', 'Croydon', '28981', '31320', '12955', '73256'], ['5', 'Newham', '37811', '15050', '7395', '60256'], ['6', 'Hackney', '27976', '19168', '9714', '56858'], ['7', 'Brent', '24391', '23723', '10518', '58632'], ['8', 'Enfield', '28222', '17334', '8131', '53687'], ['9', 'Greenwich', '35164', '8051', '5440', '48655'], ['10', 'Haringey', '23037', '18087', '6706', '47830'], ['11', 'Waltham Forest', '18815', '18841', '7135', '44791'], ['12', 'Barking and Dagenham', '28685', '5227', '3228', '37140'], ['13', 'Ealing', '17299', '13192', '6369', '36860'], ['14', 'Barnet', '19392', '4468', '3571', '27431'], ['15', 'Islington', '12622', '7943', '5729', '26294'], ['16', 'Redbridge', '12357', '9064', '3424', '24845'], ['17', 'Hammersmith and Fulham', '10552', '7111', '3842', '21505'], ['18', 'Merton', '10442', '8126', '2243', '20811'], ['19', 'Hillingdon', '11275', '4615', '4192', '20082']], 'name': 'table_19149550_7'}