def list_collaborators(self, repo):
        query = 'SELECT unnest(nspacl) FROM pg_namespace WHERE nspname=%s;'
        params = (repo, )
        res = self.execute_sql(query, params)

        # postgres privileges
        # r -- SELECT ("read")
        # w -- UPDATE ("write")
        # a -- INSERT ("append")
        # d -- DELETE
        # D -- TRUNCATE
        # x -- REFERENCES
        # t -- TRIGGER
        # X -- EXECUTE
        # U -- USAGE
        # C -- CREATE
        # c -- CONNECT
        # T -- TEMPORARY
        # arwdDxt -- ALL PRIVILEGES (for tables, varies for other objects)
        # * -- grant option for preceding privilege
        # /yyyy -- role that granted this privilege

        collaborators = []
        for row in res['tuples']:
            # for reference, rows look like this:
            # ('username=UC/repo_base',)

            collab_obj = {}
            username = row[0].split('=')[0].strip()
            permissions = row[0].split('=')[1].split('/')[0]

            collab_obj['username'] = username
            collab_obj['db_permissions'] = permissions

            collaborators.append(collab_obj)

        return collaborators