code: def get_context(self, name, value, attrs):
          
          context = super(NgWidgetMixin, self).get_context(name, value, attrs)
          if callable(getattr(self._field, 'update_widget_rendering_context', None)):
              self._field.update_widget_rendering_context(context)
          return context
docs: Some widgets require a modified rendering context, if they contain angular directives.