user: Question: What team was promoted in the Serbian League East in the same season when Kolubara was promoted in the Serbian League Belgrade?
Columns: ['Season', 'Serbian League Belgrade', 'Serbian League East', 'Serbian League Vojvodina', 'Serbian League West']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['2006–07', 'Hajduk Beograd', 'Jagodina', 'Novi Sad', 'Metalac G. Milanovac']
SQL:

assistant: SELECT "Serbian League East" FROM "Table" WHERE "Serbian League Belgrade" = 'Kolubara';