filter foreignkey field in django admin

look here http://books.agiliq.com/projects/django-admin-cookbook/en/latest/filter_fk_dropdown.html

@admin.register(Hero)
class HeroAdmin(admin.ModelAdmin, ExportCsvMixin):
    ...
    def formfield_for_foreignkey(self, db_field, request, **kwargs):
        if db_field.name == "category":
            kwargs["queryset"] = Category.objects.filter(name__in=['God', 'Demi God'])
        return super().formfield_for_foreignkey(db_field, request, **kwargs)

I actually prefer to do it in get_form like so:

Django < 2:

class CompanyAdmin(admin.ModelAdmin):
    def get_form(self, request, obj=None, **kwargs):
        form = super(CompanyAdmin, self).get_form(request, obj, **kwargs)
        form.fields['theme'].queryset = Theme.objects.filter(name__iexact='company')
        return form

Django >= 2

class CompanyAdmin(admin.ModelAdmin):
    def get_form(self, request, obj=None, **kwargs):
        form = super(CompanyAdmin, self).get_form(request, obj, **kwargs)
        form.base_fields['theme'].queryset = Theme.objects.filter(name__iexact='company')
        return form

Use the render_change_form method:

class CompanyAdmin(admin.ModelAdmin):
    def render_change_form(self, request, context, *args, **kwargs):
         context['adminform'].form.fields['theme'].queryset = Theme.objects.filter(name__iexact='company')
         return super(CompanyAdmin, self).render_change_form(request, context, *args, **kwargs)