title: How to exclude parent field that uses Select widget?
body: <p>I would like to exclude a particular field (<code>data_type</code> that uses Select widget) in the subclass that is defined in the parent form. I defined the classes like this:</p>
  
  <pre><code>class ParentForm(forms.ModelForm):
      data_type = forms.CharField(widget=forms.Select(choices=ANNOTATION_TYPES))
  
      class Meta:
          model = Annotation
          fields = ('data_value','data_type','active','primary_source')                 
          exclude = ()
  
  
  class DetailForm(ParentForm):
  
      class Meta(ParentForm.Meta):        
          exclude = ('data_type','primary_source')
  </code></pre>
  
  <p>This looks OK:</p>
  
  <pre><code>print DetailForm.Meta.exclude
  ('data_type', 'primary_source')
  </code></pre>
  
  <p>However when I print HTML I still see the field <code>data_type</code> in the <code>DetailForm</code> (and I don't see the other excluded field <code>primary_source</code>):</p>
  
  <pre><code>print DetailForm(None)
  </code></pre>
  
  <p>HTML:</p>
  
  <pre><code>&lt;tr&gt;&lt;th&gt;&lt;label for="id_data_value"&gt;Data value:&lt;/label&gt;&lt;/th&gt;..
  &lt;tr&gt;&lt;th&gt;&lt;label for="id_active"&gt;Active:&lt;/label&gt;&lt;/th&gt;....
  &lt;tr&gt;&lt;th&gt;&lt;label for="id_data_type"&gt;Data type:&lt;/label&gt;&lt;/th&gt;&lt;td&gt;
  &lt;select name="data_type" id="id_data_type"&gt;
  &lt;option value="Comment1"&gt;Subcellular location&lt;/option&gt;
  &lt;option value="Comment2"&gt;Function&lt;/option&gt;
  &lt;option value="Comment3"&gt;Sequence caution&lt;/option&gt;
  &lt;/select&gt;&lt;/td&gt;&lt;/tr&gt;
  </code></pre>
  
  <p>It looks there is a problem with the way the <code>data_type</code> is defined. Any ideas?</p>