fix sift doctest
fix sift doctest

sift now requires iterable

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