code: def answerUnsupported(self, message, preferred_association_type=None,
                            preferred_session_type=None):
          
          if self.message.isOpenID1():
              raise ProtocolError(self.message)
  
          response = OpenIDResponse(self)
          response.fields.setArg(OPENID_NS, 'error_code', 'unsupported-type')
          response.fields.setArg(OPENID_NS, 'error', message)
  
          if preferred_association_type:
              response.fields.setArg(
                  OPENID_NS, 'assoc_type', preferred_association_type)
  
          if preferred_session_type:
              response.fields.setArg(
                  OPENID_NS, 'session_type', preferred_session_type)
  
          return response
docs: Respond to this request indicating that the association
          type or association session type is not supported.