docs: def clean_publish_dates(self):
          """
          If an end_date value is provided, the start_date must be less.
          """
          if self.end_date:
              if not self.start_date:
                  raise ValidationError("""The End Date requires a Start Date value.""")
              elif self.end_date <= self.start_date:
                  raise ValidationError("""The End Date must not precede the Start Date.""")