Fix a bug in newhandlers
Fix a bug in newhandlers

The set returned by __getitem__ has to be the same set used by the
defaultdict, because of mutability.

Gadal/sympy,sahmed95/sympy,moble/sympy,yashsharan/sympy,Vishluck/sympy,shikil/sympy,wanglongqi/sympy,bukzor/sympy,MechCoder/sympy,abloomston/sympy,chaffra/sympy,moble/sympy,kevalds51/sympy,Shaswat27/sympy,asm666/sympy,saurabhjn76/sympy,maniteja123/sympy,skidzo/sympy,wanglongqi/sympy,farhaanbukhsh/sympy,hargup/sympy,abhiii5459/sympy,kumarkrishna/sympy,kaichogami/sympy,MechCoder/sympy,bukzor/sympy,kaushik94/sympy,emon10005/sympy,wanglongqi/sympy,AkademieOlympia/sympy,Gadal/sympy,garvitr/sympy,skidzo/sympy,abloomston/sympy,kaichogami/sympy,madan96/sympy,abhiii5459/sympy,oliverlee/sympy,VaibhavAgarwalVA/sympy,Vishluck/sympy,lindsayad/sympy,pandeyadarsh/sympy,chaffra/sympy,yukoba/sympy,AkademieOlympia/sympy,cswiercz/sympy,grevutiu-gabriel/sympy,Titan-C/sympy,drufat/sympy,abhiii5459/sympy,debugger22/sympy,kevalds51/sympy,ga7g08/sympy,drufat/sympy,sahmed95/sympy,MechCoder/sympy,abloomston/sympy,toolforger/sympy,hargup/sympy,atreyv/sympy,ga7g08/sympy,sampadsaha5/sympy,iamutkarshtiwari/sympy,ga7g08/sympy,hargup/sympy,Titan-C/sympy,yukoba/sympy,mafiya69/sympy,asm666/sympy,ChristinaZografou/sympy,madan96/sympy,atreyv/sympy,ahhda/sympy,aktech/sympy,jbbskinny/sympy,kevalds51/sympy,aktech/sympy,shikil/sympy,atreyv/sympy,rahuldan/sympy,jaimahajan1997/sympy,Shaswat27/sympy,mafiya69/sympy,AkademieOlympia/sympy,yashsharan/sympy,debugger22/sympy,Arafatk/sympy,jbbskinny/sympy,sahmed95/sympy,Designist/sympy,maniteja123/sympy,iamutkarshtiwari/sympy,wyom/sympy,sampadsaha5/sympy,kumarkrishna/sympy,postvakje/sympy,wyom/sympy,wyom/sympy,jerli/sympy,chaffra/sympy,Vishluck/sympy,bukzor/sympy,mcdaniel67/sympy,kaichogami/sympy,VaibhavAgarwalVA/sympy,Gadal/sympy,emon10005/sympy,sampadsaha5/sympy,Titan-C/sympy,maniteja123/sympy,lindsayad/sympy,farhaanbukhsh/sympy,postvakje/sympy,grevutiu-gabriel/sympy,cswiercz/sympy,yukoba/sympy,ChristinaZografou/sympy,postvakje/sympy,Curious72/sympy,iamutkarshtiwari/sympy,Curious72/sympy,oliverlee/sympy,atsao72/sympy,toolforger/sympy,kaushik94/sympy,Arafatk/sympy,jaimahajan1997/sympy,garvitr/sympy,VaibhavAgarwalVA/sympy,ahhda/sympy,souravsingh/sympy,jbbskinny/sympy,farhaanbukhsh/sympy,debugger22/sympy,atsao72/sympy,mcdaniel67/sympy,Designist/sympy,lindsayad/sympy,atsao72/sympy,kumarkrishna/sympy,Davidjohnwilson/sympy,skidzo/sympy,yashsharan/sympy,oliverlee/sympy,saurabhjn76/sympy,moble/sympy,emon10005/sympy,drufat/sympy,mafiya69/sympy,kaushik94/sympy,souravsingh/sympy,souravsingh/sympy,Curious72/sympy,Arafatk/sympy,Davidjohnwilson/sympy,rahuldan/sympy,toolforger/sympy,pandeyadarsh/sympy,ahhda/sympy,pandeyadarsh/sympy,jerli/sympy,garvitr/sympy,shikil/sympy,asm666/sympy,rahuldan/sympy,grevutiu-gabriel/sympy,Designist/sympy,madan96/sympy,jaimahajan1997/sympy,aktech/sympy,Shaswat27/sympy,saurabhjn76/sympy,ChristinaZografou/sympy,jerli/sympy,mcdaniel67/sympy,Davidjohnwilson/sympy,cswiercz/sympy