Small fix in NO.remove_brackets()
Small fix in NO.remove_brackets()

For consistency we want to avoid creating an index with
both 'above_fermi=False' and 'below_fermi=True'.

Added some comments

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