class_docstr: Abstract base class for protocol messages.
  
  Protocol message classes are almost always generated by the protocol
  compiler.  These generated types subclass Message and implement the methods
  shown below.
docstr: Merges serialized protocol buffer data into this message.
  
  When we find a field in `serialized` that is already present
  in this message:
  
  -   If it's a "repeated" field, we append to the end of our list.
  -   Else, if it's a scalar, we overwrite our field.
  -   Else, (it's a nonrepeated composite), we recursively merge
      into the existing composite.
  
  Args:
    serialized (bytes): Any object that allows us to call
      ``memoryview(serialized)`` to access a string of bytes using the
      buffer interface.
  
  Returns:
    int: The number of bytes read from `serialized`.
    For non-group messages, this will always be `len(serialized)`,
    but for messages which are actually groups, this will
    generally be less than `len(serialized)`, since we must
    stop when we reach an ``END_GROUP`` tag.  Note that if
    we *do* stop because of an ``END_GROUP`` tag, the number
    of bytes returned does not include the bytes
    for the ``END_GROUP`` tag information.
  
  Raises:
    DecodeError: if the input cannot be parsed.
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code: def MergeFromString(self, serialized):
      """Merges serialized protocol buffer data into this message.
  
      When we find a field in `serialized` that is already present
      in this message:
  
      -   If it's a "repeated" field, we append to the end of our list.
      -   Else, if it's a scalar, we overwrite our field.
      -   Else, (it's a nonrepeated composite), we recursively merge
          into the existing composite.
  
      Args:
        serialized (bytes): Any object that allows us to call
          ``memoryview(serialized)`` to access a string of bytes using the
          buffer interface.
  
      Returns:
        int: The number of bytes read from `serialized`.
        For non-group messages, this will always be `len(serialized)`,
        but for messages which are actually groups, this will
        generally be less than `len(serialized)`, since we must
        stop when we reach an ``END_GROUP`` tag.  Note that if
        we *do* stop because of an ``END_GROUP`` tag, the number
        of bytes returned does not include the bytes
        for the ``END_GROUP`` tag information.
  
      Raises:
        DecodeError: if the input cannot be parsed.
      """
      # TODO(robinson): Document handling of unknown fields.
      # TODO(robinson): When we switch to a helper, this will return None.
      raise NotImplementedError
  
label_desc: Use image node_id 12 for calling the Message obj's underlying member method code with example usage: obj.MergeFromString(serialized) without return types