How to use the pathos.util._b function in pathos

def onChild(pid, fromparent, toparent):
        toparent.write(_b('hello dad\n'))
        toparent.flush()
        s = _str(fromparent.readline())
        print(s, end='')
        os._exit(0)

def onParent(pid, fromchild, tochild):
        s = _str(fromchild.readline())
        print(s, end='')
        tochild.write(_b('hello son\n'))
        tochild.flush()
        os.wait()

def onChild(pid, fromparent, toparent):
            try:
                response = self._server._marshaled_dispatch(data)
                self._sendResponse(response)
                line = _str(fromparent.readline())
                toparent.write(_b('done\n'))
                toparent.flush()
            except:
                logger(name='pathos.xmlrpc', level=30).error(print_exc_info())
            os._exit(0)

def _sendResponse(self, response):
        """ Write the XML-RPC response """

        response = _b(response)
        self.send_response(200)
        self.send_header("Content-type", "text/xml")
        self.send_header("Content-length", str(len(response)))
        self.end_headers()
        self.wfile.write(response)
        self.wfile.flush()
        self.connection.shutdown(1)

def onParent(pid, fromchild, tochild):
            self._server._registerChild(pid, fromchild)
            tochild.write(_b('done\n'))
            tochild.flush()

response = dispatch_method(method, params)
            else:
                response = self._dispatch(method, params)
            # wrap response in a singleton tuple
            response = (response,)
            response = client.dumps(response, methodresponse=1)
        except Fault as fault: # breaks 2.5 compatibility
            fault.faultString = print_exc_info()
            response = client.dumps(fault)
        except:
            # report exception back to server
            response = client.dumps(
                client.Fault(1, "\n%s" % print_exc_info())
                )

        return _b(response)