title: getting error message Enter a list of values(validation using django forms)
body: <p>I am using <code>MultipleChoiceField</code> and already mentioned <code>required=False</code>. Then Why I am getting this error <code>Username:  Enter a list of values</code>.</p>
  
  <pre><code>def get_my_choices():
    users = User.query()
    choices_list = [(x.key.id(), x.email) for x in users]
    return choices_list
  
  class MyForm(forms.Form):
    username = forms.MultipleChoiceField(required=False, choices=get_my_choices())
  </code></pre>
  
  <p>Am I doing something wrong? thanks :-)</p>