added an inheritance test
added an inheritance test

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