fix doctest in Poisson
fix doctest in Poisson

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