code: def validate(self, value, model_instance):
          
          # pylint: disable=newstyle
          super(TimeZoneField, self).validate(
              value=self.get_prep_value(value),
              model_instance=model_instance
          )
  
          # Insure the value is can be converted to a timezone
          self.to_python(value)
docs: Validates value and throws ValidationError. Subclasses should override
          this to provide validation logic.