def get_collaborators(self, affiliation=github.GithubObject.NotSet):
        """
        :calls: `GET /repos/:owner/:repo/collaborators <http://developer.github.com/v3/repos/collaborators>`_
        :param affiliation: string
        :rtype: :class:`github.PaginatedList.PaginatedList` of :class:`github.NamedUser.NamedUser`
        """

        url_parameters = dict()
        allowed_affiliations = ['outside', 'direct', 'all']
        if affiliation is not github.GithubObject.NotSet:
            assert isinstance(affiliation, str), affiliation
            assert affiliation in allowed_affiliations, \
                'Affiliation can be one of ' + ', '.join(allowed_affiliations)
            url_parameters['affiliation'] = affiliation

        return github.PaginatedList.PaginatedList(
            github.NamedUser.NamedUser,
            self._requester,
            self.url + "/collaborators",
            url_parameters
        )