code: def get_dataset_date(self, date_format=None):
          # type: (Optional[str]) -> Optional[str]
          
          dataset_date = self.get_dataset_date_as_datetime()
          return self._get_formatted_date(dataset_date, date_format)
docs: Get dataset date as string in specified format. For range returns start date.
          If no format is supplied, an ISO 8601 string is returned.
  
          Args:
              date_format (Optional[str]): Date format. None is taken to be ISO 8601. Defaults to None.
  
          Returns:
              Optional[str]: Dataset date string or None if no date is set