added assertion to check that mappers only inherit from a mapper with the same "primary/non-primary" setting
added assertion to check that mappers only inherit from a mapper with the same "primary/non-primary" setting

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