simplify Mul.is_(positive|negative) code; add docstrings
simplify Mul.is_(positive|negative) code; add docstrings

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