code: def ballot_id(self):
          
          self._validate()
          self._validate_division(self.division)
          self._validate_for_ballot_id()
  
          parts = []
          parts.append(self.election_type)
          if self.subtype:
              parts.append(self.subtype)
          if self.organisation:
              parts.append(self.organisation)
          if self.division:
              parts.append(self.division)
          if self.contest_type:
              parts.append(self.contest_type)
          parts.append(self.date)
          return ".".join(parts)
docs: str: Ballot ID