Write the tests for categories.Object and categories.Morphism.
Write the tests for categories.Object and categories.Morphism.

The tests do not pass at the moment.  The goal is to define the desired
behaviour of the methods in Morphism by means of tests.

beni55/sympy,Titan-C/sympy,drufat/sympy,asm666/sympy,pbrady/sympy,beni55/sympy,farhaanbukhsh/sympy,lindsayad/sympy,sampadsaha5/sympy,jaimahajan1997/sympy,madan96/sympy,abhiii5459/sympy,chaffra/sympy,lindsayad/sympy,yashsharan/sympy,atreyv/sympy,saurabhjn76/sympy,Curious72/sympy,ChristinaZografou/sympy,sahilshekhawat/sympy,atsao72/sympy,mcdaniel67/sympy,jerli/sympy,pandeyadarsh/sympy,ga7g08/sympy,jbbskinny/sympy,toolforger/sympy,kumarkrishna/sympy,souravsingh/sympy,kaichogami/sympy,jerli/sympy,iamutkarshtiwari/sympy,cccfran/sympy,moble/sympy,vipulroxx/sympy,Sumith1896/sympy,rahuldan/sympy,bukzor/sympy,kmacinnis/sympy,jerli/sympy,sahilshekhawat/sympy,drufat/sympy,shipci/sympy,Curious72/sympy,Arafatk/sympy,wanglongqi/sympy,chaffra/sympy,skidzo/sympy,hrashk/sympy,VaibhavAgarwalVA/sympy,garvitr/sympy,shikil/sympy,grevutiu-gabriel/sympy,mafiya69/sympy,bukzor/sympy,yashsharan/sympy,farhaanbukhsh/sympy,Designist/sympy,toolforger/sympy,pbrady/sympy,saurabhjn76/sympy,sunny94/temp,cswiercz/sympy,kaushik94/sympy,Mitchkoens/sympy,atsao72/sympy,cswiercz/sympy,grevutiu-gabriel/sympy,kevalds51/sympy,saurabhjn76/sympy,Shaswat27/sympy,Mitchkoens/sympy,lindsayad/sympy,aktech/sympy,diofant/diofant,jbbskinny/sympy,hargup/sympy,garvitr/sympy,sampadsaha5/sympy,Titan-C/sympy,Sumith1896/sympy,vipulroxx/sympy,debugger22/sympy,jaimahajan1997/sympy,hargup/sympy,aktech/sympy,emon10005/sympy,AkademieOlympia/sympy,MechCoder/sympy,wyom/sympy,yashsharan/sympy,ChristinaZografou/sympy,hrashk/sympy,Vishluck/sympy,shikil/sympy,kaushik94/sympy,liangjiaxing/sympy,kaushik94/sympy,jamesblunt/sympy,toolforger/sympy,wanglongqi/sympy,wyom/sympy,Gadal/sympy,dqnykamp/sympy,pbrady/sympy,kmacinnis/sympy,Vishluck/sympy,moble/sympy,srjoglekar246/sympy,lidavidm/sympy,Davidjohnwilson/sympy,madan96/sympy,jaimahajan1997/sympy,shipci/sympy,ahhda/sympy,garvitr/sympy,ahhda/sympy,asm666/sympy,AunShiLord/sympy,sampadsaha5/sympy,oliverlee/sympy,farhaanbukhsh/sympy,dqnykamp/sympy,grevutiu-gabriel/sympy,amitjamadagni/sympy,moble/sympy,AunShiLord/sympy,Gadal/sympy,iamutkarshtiwari/sympy,sahmed95/sympy,VaibhavAgarwalVA/sympy,cccfran/sympy,rahuldan/sympy,ga7g08/sympy,abloomston/sympy,maniteja123/sympy,yukoba/sympy,pandeyadarsh/sympy,mafiya69/sympy,kevalds51/sympy,maniteja123/sympy,debugger22/sympy,skirpichev/omg,cswiercz/sympy,MridulS/sympy,shikil/sympy,bukzor/sympy,Titan-C/sympy,shipci/sympy,maniteja123/sympy,mcdaniel67/sympy,ga7g08/sympy,skidzo/sympy,Davidjohnwilson/sympy,vipulroxx/sympy,souravsingh/sympy,AkademieOlympia/sympy,oliverlee/sympy,meghana1995/sympy,asm666/sympy,VaibhavAgarwalVA/sympy,kmacinnis/sympy,Designist/sympy,Vishluck/sympy,MridulS/sympy,kumarkrishna/sympy,postvakje/sympy,amitjamadagni/sympy,MridulS/sympy,kumarkrishna/sympy,pandeyadarsh/sympy,skidzo/sympy,beni55/sympy,Sumith1896/sympy,abhiii5459/sympy,AkademieOlympia/sympy,flacjacket/sympy,atreyv/sympy,aktech/sympy,postvakje/sympy,Gadal/sympy,souravsingh/sympy,MechCoder/sympy,sahmed95/sympy,debugger22/sympy,madan96/sympy,iamutkarshtiwari/sympy,kaichogami/sympy,cccfran/sympy,Shaswat27/sympy,postvakje/sympy,Davidjohnwilson/sympy,hargup/sympy,lidavidm/sympy,Shaswat27/sympy,jbbskinny/sympy,Designist/sympy,abhiii5459/sympy,emon10005/sympy,meghana1995/sympy,abloomston/sympy,yukoba/sympy,sahmed95/sympy,atreyv/sympy,Arafatk/sympy,hrashk/sympy,atsao72/sympy,Curious72/sympy,sahilshekhawat/sympy,wanglongqi/sympy,jamesblunt/sympy,oliverlee/sympy,emon10005/sympy,sunny94/temp,ChristinaZografou/sympy,drufat/sympy,liangjiaxing/sympy,wyom/sympy,meghana1995/sympy,Arafatk/sympy,kaichogami/sympy,AunShiLord/sympy,lidavidm/sympy,jamesblunt/sympy,chaffra/sympy,mcdaniel67/sympy,yukoba/sympy,sunny94/temp,rahuldan/sympy,MechCoder/sympy,abloomston/sympy,ahhda/sympy,dqnykamp/sympy,liangjiaxing/sympy,Mitchkoens/sympy,mafiya69/sympy,kevalds51/sympy