title: MultipleChoiceField not showing stored values in Django Admin
body: <p>How do you get a MultipleChoiceField() to correctly load initial values?</p>
  
  <p>I have a Django model with a CharField, which I'm rendering in admin as a MultipleChoiceField() because I want to limit its value to one or more specific choices.</p>
  
  <p>My code looks something like:</p>
  
  <pre><code>class MyModelInlineForm(ModelForm):
  
      my_text_field = forms.MultipleChoiceField(required=False)
  
      def __init__(self, *args, **kwargs):
          super(MyModelInlineForm, self).__init__(*args, **kwargs)
  
          self.fields['my_text_field'].choices = get_choices(self.instance)
  
          if self.instance:
              self.fields['my_text_field'].initial = self.instance.my_text_field
  
  class MyModelInline(admin.TabularInline):
      model = MyModel
      form = MyModelInlineForm
      extra = 0
  </code></pre>
  
  <p>It seems to render fine, but when I select values and save, the new form loads with no values selected. I've confirmed the value is being correctly saved in the database, but the form isn't loading it, and I'm not sure why.</p>
  
  <p>Based on some <a href="https://stackoverflow.com/questions/2425668/django-forms-multiplechoicefield-reverts-to-original-value-on-save">similar</a> <a href="https://stackoverflow.com/questions/488036/django-modelmultiplechoicefield-doesnt-select-initial-choices">questions</a>, I tried explicitly setting the <code>initial</code> value of my model's saved field, but this appeared to have no effect.</p>
  
  <p>What am I doing wrong?</p>