substitute_dummies should also accept single term expressions.
substitute_dummies should also accept single term expressions.

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