code: def get_form(self, request, obj=None, **kwargs):
          
          kwargs.update(widgets={
              'plugin_type': widgets.Select(choices=self.plugins_for_site),
              'css_classes': JSONMultiWidget(self.classname_fields),
              'inline_styles': JSONMultiWidget(self.style_fields)
          })
          form = super(PluginExtraFieldsAdmin, self).get_form(request, obj, **kwargs)
          rectify_partial_form_field(form.base_fields['css_classes'], self.classname_fields)
          form.classname_fields = self.classname_fields
          rectify_partial_form_field(form.base_fields['inline_styles'], self.style_fields)
          form.style_fields = self.style_fields
          return form
docs: Build the form used for changing the model.