Adds documentation to Query.slice().
Adds documentation to Query.slice().

sqlalchemy/sqlalchemy,graingert/sqlalchemy,zzzeek/sqlalchemy,monetate/sqlalchemy,j5int/sqlalchemy,wujuguang/sqlalchemy,wujuguang/sqlalchemy,sandan/sqlalchemy,graingert/sqlalchemy,robin900/sqlalchemy,bdupharm/sqlalchemy,j5int/sqlalchemy,sandan/sqlalchemy,monetate/sqlalchemy,bdupharm/sqlalchemy,robin900/sqlalchemy