code: def pack(self, value=None):
          
          if isinstance(value, type(self)):
              return value.pack()
  
          if value is None:
              value = self
          else:
              container = type(self)(items=None)
              container.extend(value)
              value = container
  
          bin_message = b''
          try:
              for item in value:
                  bin_message += item.pack()
              return bin_message
          except exceptions.PackException as err:
              msg = "{} pack error: {}".format(type(self).__name__, err)
              raise exceptions.PackException(msg)
docs: Pack the value as a binary representation.
  
          Returns:
              bytes: The binary representation.