user: Question: Sport of Football, and a Venue of Stadion Polonii is what league?
Columns: ['Club', 'Sport', 'Founded', 'League', 'Venue', 'Head Coach']
Types: ['text', 'text', 'real', 'text', 'text', 'text']
Sample row: ['Legia Warszawa (Polish) [ dead link ]', 'Football', 1916.0, 'Ekstraklasa', 'Pepsi Arena', 'Jan Urban']
SQL:

assistant: SELECT "League" FROM "Table" WHERE "Sport" = 'Football' AND "Venue" = 'Stadion Polonii';