docs: def _Aff4Size(aff4_obj):
    """Retrieves the total size in bytes of an AFF4 object.
  
    Args:
      aff4_obj: An AFF4 stream instance to retrieve size for.
  
    Returns:
      An integer representing number of bytes.
  
    Raises:
      TypeError: If `aff4_obj` is not an instance of AFF4 stream.
    """
    if not isinstance(aff4_obj, aff4.AFF4Stream):
      message = "Expected an instance of `%s` but received `%s`"
      raise TypeError(message % (aff4.AFF4Stream, type(aff4_obj)))
  
    return int(aff4_obj.Get(aff4_obj.Schema.SIZE))