code: def receive():
      
      header = _in_file.read(8)
      logging.getLogger(__name__).debug('Received command, header: [%s]' % header)
      if header is None or len(header) < 8:
          # Pipe EOF encountered
          logging.getLogger(__name__).debug('Pipe EOF encountered')
          return None, None
      length = int(header[2:])
      data = _in_file.read(length)
      command = CommandType(header[:2])
      data = data.decode('utf8')
      logging.getLogger(__name__).debug('Received command, data: [%s]' % data)
      return command, data
docs: Receive a command from Training Service.
      Returns a tuple of command (CommandType) and payload (str)