docs: def set_custom_value(self, field_name, value):
          """ Set a value for a specified custom field
          field_name - Name of the custom field you want.
          value - Value to set it to
          """
          custom_field = self.get_custom_field(field_name)
          custom_value = CustomFieldValue.objects.get_or_create(
              field=custom_field, object_id=self.id)[0]
          custom_value.value = value
          custom_value.save()