code: def connect(self, username=None, passcode=None, wait=False, headers=None, **keyword_headers):
          
          cmd = CMD_STOMP
          headers = utils.merge_headers([headers, keyword_headers])
          headers[HDR_ACCEPT_VERSION] = self.version
  
          if self.transport.vhost:
              headers[HDR_HOST] = self.transport.vhost
  
          if username is not None:
              headers[HDR_LOGIN] = username
  
          if passcode is not None:
              headers[HDR_PASSCODE] = passcode
  
          self.send_frame(cmd, headers)
  
          if wait:
              self.transport.wait_for_connection()
              if self.transport.connection_error:
                  raise ConnectFailedException()
docs: Start a connection.
  
          :param str username: the username to connect with
          :param str passcode: the password used to authenticate with
          :param bool wait: if True, wait for the connection to be established/acknowledged
          :param dict headers: a map of any additional headers the broker requires
          :param keyword_headers: any additional headers the broker requires