zerver/lib/statistics.py: Fix annotations.
zerver/lib/statistics.py: Fix annotations.

Add type annotation to a variable.
Use abstract base container types where suitable.
Add missing imports from typing.

KingxBanana/zulip,reyha/zulip,amyliu345/zulip,vabs22/zulip,jrowan/zulip,niftynei/zulip,mahim97/zulip,timabbott/zulip,vikas-parashar/zulip,vaidap/zulip,SmartPeople/zulip,vabs22/zulip,aakash-cr7/zulip,blaze225/zulip,isht3/zulip,shubhamdhama/zulip,susansls/zulip,grave-w-grave/zulip,AZtheAsian/zulip,zacps/zulip,kou/zulip,kou/zulip,rht/zulip,TigorC/zulip,souravbadami/zulip,timabbott/zulip,jphilipsen05/zulip,synicalsyntax/zulip,dawran6/zulip,punchagan/zulip,Jianchun1/zulip,andersk/zulip,showell/zulip,JPJPJPOPOP/zulip,arpith/zulip,jainayush975/zulip,amanharitsh123/zulip,amanharitsh123/zulip,Diptanshu8/zulip,aakash-cr7/zulip,cosmicAsymmetry/zulip,samatdav/zulip,zulip/zulip,dawran6/zulip,ahmadassaf/zulip,shubhamdhama/zulip,eeshangarg/zulip,hackerkid/zulip,krtkmj/zulip,aakash-cr7/zulip,KingxBanana/zulip,shubhamdhama/zulip,jrowan/zulip,mohsenSy/zulip,ahmadassaf/zulip,Galexrt/zulip,hackerkid/zulip,reyha/zulip,showell/zulip,PhilSk/zulip,punchagan/zulip,JPJPJPOPOP/zulip,dhcrzf/zulip,Jianchun1/zulip,sup95/zulip,dattatreya303/zulip,KingxBanana/zulip,ryanbackman/zulip,shubhamdhama/zulip,zacps/zulip,Juanvulcano/zulip,verma-varsha/zulip,brainwane/zulip,SmartPeople/zulip,TigorC/zulip,rishig/zulip,arpith/zulip,showell/zulip,j831/zulip,brockwhittaker/zulip,vaidap/zulip,punchagan/zulip,sharmaeklavya2/zulip,sup95/zulip,andersk/zulip,vikas-parashar/zulip,sonali0901/zulip,synicalsyntax/zulip,AZtheAsian/zulip,christi3k/zulip,timabbott/zulip,amanharitsh123/zulip,showell/zulip,jackrzhang/zulip,Galexrt/zulip,niftynei/zulip,andersk/zulip,samatdav/zulip,Juanvulcano/zulip,dawran6/zulip,ahmadassaf/zulip,JPJPJPOPOP/zulip,Galexrt/zulip,timabbott/zulip,sonali0901/zulip,mohsenSy/zulip,tommyip/zulip,vaidap/zulip,peguin40/zulip,sharmaeklavya2/zulip,Diptanshu8/zulip,brainwane/zulip,tommyip/zulip,kou/zulip,cosmicAsymmetry/zulip,hackerkid/zulip,grave-w-grave/zulip,ryanbackman/zulip,synicalsyntax/zulip,vikas-parashar/zulip,verma-varsha/zulip,tommyip/zulip,sonali0901/zulip,isht3/zulip,amyliu345/zulip,cosmicAsymmetry/zulip,dhcrzf/zulip,eeshangarg/zulip,timabbott/zulip,calvinleenyc/zulip,kou/zulip,grave-w-grave/zulip,krtkmj/zulip,ryanbackman/zulip,Juanvulcano/zulip,sonali0901/zulip,arpith/zulip,eeshangarg/zulip,brockwhittaker/zulip,sonali0901/zulip,joyhchen/zulip,souravbadami/zulip,hackerkid/zulip,SmartPeople/zulip,christi3k/zulip,blaze225/zulip,Galexrt/zulip,ryanbackman/zulip,vikas-parashar/zulip,umkay/zulip,Diptanshu8/zulip,susansls/zulip,Galexrt/zulip,dattatreya303/zulip,joyhchen/zulip,peguin40/zulip,vaidap/zulip,tommyip/zulip,joyhchen/zulip,mohsenSy/zulip,mahim97/zulip,Juanvulcano/zulip,shubhamdhama/zulip,vabs22/zulip,amyliu345/zulip,synicalsyntax/zulip,amyliu345/zulip,Jianchun1/zulip,kou/zulip,jrowan/zulip,samatdav/zulip,paxapy/zulip,punchagan/zulip,jainayush975/zulip,shubhamdhama/zulip,AZtheAsian/zulip,susansls/zulip,rht/zulip,paxapy/zulip,showell/zulip,ryanbackman/zulip,mohsenSy/zulip,cosmicAsymmetry/zulip,blaze225/zulip,krtkmj/zulip,eeshangarg/zulip,dhcrzf/zulip,dawran6/zulip,Jianchun1/zulip,kou/zulip,peguin40/zulip,synicalsyntax/zulip,sharmaeklavya2/zulip,jrowan/zulip,souravbadami/zulip,christi3k/zulip,jphilipsen05/zulip,grave-w-grave/zulip,isht3/zulip,blaze225/zulip,rishig/zulip,PhilSk/zulip,Juanvulcano/zulip,dhcrzf/zulip,verma-varsha/zulip,jrowan/zulip,synicalsyntax/zulip,sharmaeklavya2/zulip,vabs22/zulip,peguin40/zulip,paxapy/zulip,sup95/zulip,reyha/zulip,PhilSk/zulip,SmartPeople/zulip,KingxBanana/zulip,amyliu345/zulip,hackerkid/zulip,hackerkid/zulip,zacps/zulip,jphilipsen05/zulip,ryanbackman/zulip,KingxBanana/zulip,paxapy/zulip,blaze225/zulip,AZtheAsian/zulip,mahim97/zulip,isht3/zulip,brainwane/zulip,dattatreya303/zulip,calvinleenyc/zulip,eeshangarg/zulip,jackrzhang/zulip,dattatreya303/zulip,Diptanshu8/zulip,zacps/zulip,susansls/zulip,niftynei/zulip,jackrzhang/zulip,brockwhittaker/zulip,synicalsyntax/zulip,JPJPJPOPOP/zulip,SmartPeople/zulip,sonali0901/zulip,calvinleenyc/zulip,TigorC/zulip,cosmicAsymmetry/zulip,PhilSk/zulip,brainwane/zulip,niftynei/zulip,zulip/zulip,amanharitsh123/zulip,tommyip/zulip,andersk/zulip,calvinleenyc/zulip,Galexrt/zulip,Jianchun1/zulip,showell/zulip,niftynei/zulip,peguin40/zulip,joyhchen/zulip,blaze225/zulip,reyha/zulip,paxapy/zulip,brockwhittaker/zulip,JPJPJPOPOP/zulip,umkay/zulip,krtkmj/zulip,dhcrzf/zulip,andersk/zulip,tommyip/zulip,jackrzhang/zulip,jphilipsen05/zulip,grave-w-grave/zulip,joyhchen/zulip,christi3k/zulip,krtkmj/zulip,zulip/zulip,zulip/zulip,brainwane/zulip,jainayush975/zulip,souravbadami/zulip,zulip/zulip,rishig/zulip,Juanvulcano/zulip,aakash-cr7/zulip,samatdav/zulip,rht/zulip,ahmadassaf/zulip,joyhchen/zulip,JPJPJPOPOP/zulip,umkay/zulip,jackrzhang/zulip,jrowan/zulip,susansls/zulip,j831/zulip,vikas-parashar/zulip,peguin40/zulip,TigorC/zulip,dattatreya303/zulip,hackerkid/zulip,j831/zulip,umkay/zulip,mohsenSy/zulip,samatdav/zulip,andersk/zulip,j831/zulip,KingxBanana/zulip,reyha/zulip,zulip/zulip,punchagan/zulip,mohsenSy/zulip,brockwhittaker/zulip,jainayush975/zulip,vikas-parashar/zulip,verma-varsha/zulip,PhilSk/zulip,jphilipsen05/zulip,dawran6/zulip,mahim97/zulip,punchagan/zulip,shubhamdhama/zulip,SmartPeople/zulip,brainwane/zulip,christi3k/zulip,jainayush975/zulip,Diptanshu8/zulip,souravbadami/zulip,vabs22/zulip,TigorC/zulip,amyliu345/zulip,zacps/zulip,sup95/zulip,eeshangarg/zulip,rishig/zulip,kou/zulip,christi3k/zulip,souravbadami/zulip,isht3/zulip,calvinleenyc/zulip,cosmicAsymmetry/zulip,Jianchun1/zulip,jphilipsen05/zulip,dhcrzf/zulip,jackrzhang/zulip,vaidap/zulip,arpith/zulip,sharmaeklavya2/zulip,rht/zulip,AZtheAsian/zulip,mahim97/zulip,brainwane/zulip,zacps/zulip,amanharitsh123/zulip,tommyip/zulip,arpith/zulip,showell/zulip,eeshangarg/zulip,Galexrt/zulip,punchagan/zulip,jainayush975/zulip,aakash-cr7/zulip,rishig/zulip,dattatreya303/zulip,verma-varsha/zulip,rishig/zulip,umkay/zulip,timabbott/zulip,samatdav/zulip,sup95/zulip,verma-varsha/zulip,timabbott/zulip,aakash-cr7/zulip,rishig/zulip,krtkmj/zulip,dhcrzf/zulip,zulip/zulip,PhilSk/zulip,Diptanshu8/zulip,TigorC/zulip,ahmadassaf/zulip,jackrzhang/zulip,paxapy/zulip,umkay/zulip,j831/zulip,arpith/zulip,rht/zulip,rht/zulip,sup95/zulip,andersk/zulip,dawran6/zulip,ahmadassaf/zulip,vabs22/zulip,j831/zulip,krtkmj/zulip,niftynei/zulip,mahim97/zulip,rht/zulip,grave-w-grave/zulip,amanharitsh123/zulip,calvinleenyc/zulip,isht3/zulip,ahmadassaf/zulip,sharmaeklavya2/zulip,susansls/zulip,brockwhittaker/zulip,reyha/zulip,AZtheAsian/zulip,vaidap/zulip,umkay/zulip