class call in square brackets in django, python -

this snippet djangoproject.com tutorial. can explain why line written in way:

inlines =[choiceinline]  

instead of

inlines = choiceinline 

why there square brackets around class choiceinline?

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from django.contrib import admin naslovnica.models import poll naslovnica.models import choice  class choiceinline(admin.tabularinline):     model = choice     = 3  class polladmin(admin.modeladmin):     fieldsets = [     (none,               {'fields': ['question']}),     ('date information', {'fields': ['pub_date'], 'classes': ['collapse']}),     ]     inlines =[choiceinline]     list_display = ('question', 'pub_date', 'was_published_recently')     search_fields = ['question']     list_filter = ['pub_date']  admin.site.register(poll, polladmin) 

inlines =[choiceinline] not calling of class. create new list has class first element.

class calling done choiceinline().