- document that joinedload/eagerload work with of_type() + with_polymoprhic()
- document that joinedload/eagerload work with of_type() + with_polymoprhic()

276361270/sqlalchemy,EvaSDK/sqlalchemy,dstufft/sqlalchemy,elelianghh/sqlalchemy,graingert/sqlalchemy,olemis/sqlalchemy,Akrog/sqlalchemy,davidjb/sqlalchemy,WinterNis/sqlalchemy,davidfraser/sqlalchemy,zzzeek/sqlalchemy,bdupharm/sqlalchemy,hsum/sqlalchemy,hsum/sqlalchemy,davidjb/sqlalchemy,halfcrazy/sqlalchemy,bootandy/sqlalchemy,j5int/sqlalchemy,bdupharm/sqlalchemy,itkovian/sqlalchemy,sandan/sqlalchemy,wujuguang/sqlalchemy,davidfraser/sqlalchemy,itkovian/sqlalchemy,brianv0/sqlalchemy,epa/sqlalchemy,sandan/sqlalchemy,Akrog/sqlalchemy,wujuguang/sqlalchemy,ThiefMaster/sqlalchemy,halfcrazy/sqlalchemy,pdufour/sqlalchemy,epa/sqlalchemy,robin900/sqlalchemy,WinterNis/sqlalchemy,brianv0/sqlalchemy,sqlalchemy/sqlalchemy,monetate/sqlalchemy,monetate/sqlalchemy,ThiefMaster/sqlalchemy,pdufour/sqlalchemy,graingert/sqlalchemy,robin900/sqlalchemy,bootandy/sqlalchemy,EvaSDK/sqlalchemy,inspirehep/sqlalchemy,elelianghh/sqlalchemy,dstufft/sqlalchemy,inspirehep/sqlalchemy,276361270/sqlalchemy,olemis/sqlalchemy,j5int/sqlalchemy,wfxiang08/sqlalchemy,wfxiang08/sqlalchemy