docs: def WriteGRRUser(self,
                     username,
                     password=None,
                     ui_mode=None,
                     canary_mode=None,
                     user_type=None):
      """Writes user object for a user with a given name."""
      u = self.users.setdefault(username, rdf_objects.GRRUser(username=username))
      if password is not None:
        u.password = password
      if ui_mode is not None:
        u.ui_mode = ui_mode
      if canary_mode is not None:
        u.canary_mode = canary_mode
      if user_type is not None:
        u.user_type = user_type