Unifying univarate and multivarite code in Order.contains().
Unifying univarate and multivarite code in Order.contains().

This doesn't affect performance and makes the code simpler.

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