tweak checksol and add some comments
tweak checksol and add some comments

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