fix docstrings in expressions.rst
fix docstrings in expressions.rst

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