How to pass multichoicefiled values ​​to initial?

Question

Django

The search form has a multiple choice field. It is necessary that the form, when clicking on the search, does not dump the previously entered values, for this, with the usual fields (select), I do this

if 'type_of_container' in request.GET and request.GET['type_of_container'] != '':
        type_of_container = get_object_or_404(Typeofcontainer, id=request.GET['type_of_container'])
    else:
        type_of_container = None

form = CityChoiceForm(initial={
        'type_of_container':type_of_container,
        })

If a multiple choice field is done in the same way, it saves the last selected checkbox. That's why I do it

if 'type_of_body' in request.GET and request.GET.getlist('type_of_body') != '':
         type_of_body  = get_list_or_404(Typeofbody, id__in=request.GET.getlist('type_of_body'))
    else:
        type_of_body = None
form = CityChoiceForm(initial={
        'type_of_body':type_of_body,
        })

but in the form an empty value is obtained.