code: def recv_data(self, control_frame=False):
          
          opcode, frame = self.recv_data_frame(control_frame)
          return opcode, frame.data
docs: Receive data with operation code.
  
          control_frame: a boolean flag indicating whether to return control frame
          data, defaults to False
  
          return  value: tuple of operation code and string(byte array) value.