docs: def get_publication_date(self, **kwargs):
          """Determine the creation date for the publication date."""
          date_string = kwargs.get('content', '')
          date_match = CREATION_DATE_REGEX.match(date_string)
          month_match = CREATION_MONTH_REGEX.match(date_string)
          year_match = CREATION_YEAR_REGEX.match(date_string)
          # Check if a date match exists.
          if date_match:
              (year, month, day) = date_match.groups('')
              # Create the date.
              try:
                  creation_date = datetime.date(int(year), int(month), int(day))
              except ValueError:
                  return None
              else:
                  return '%s/%s/%s' % (
                      format_date_string(creation_date.month),
                      format_date_string(creation_date.day),
                      creation_date.year,
                  )
          elif month_match:
              (year, month) = month_match.groups('')
              # Create the date.
              try:
                  creation_date = datetime.date(int(year), int(month), 1)
              except ValueError:
                  return None
              else:
                  return '%s/%s' % (
                      format_date_string(creation_date.month),
                      creation_date.year,
                  )
          elif year_match:
              year = year_match.groups('')[0]
              return year
          else:
              return None