Add an organisation segment.

        Args:
            organisation (str): Official name of an administrative body
                holding an election.

        Returns:
            IdBuilder

        Raises:
            ValueError

def with_organisation(self, organisation):
        """Add an organisation segment.

        Args:
            organisation (str): Official name of an administrative body
                holding an election.

        Returns:
            IdBuilder

        Raises:
            ValueError
        """
        if organisation is None:
            organisation = ''
        organisation = slugify(organisation)
        self._validate_organisation(organisation)
        self.organisation = organisation
        return self