code: def _Aff4Read(aff4_obj, offset, length):
    
    length = length or (_Aff4Size(aff4_obj) - offset)
  
    aff4_obj.Seek(offset)
    return aff4_obj.Read(length)
docs: Reads contents of given AFF4 file.
  
    Args:
      aff4_obj: An AFF4 stream instance to retrieve contents for.
      offset: An offset to start the reading from.
      length: A number of bytes to read. Reads the whole file if 0.
  
    Returns:
      Contents of specified AFF4 stream.
  
    Raises:
      TypeError: If `aff4_obj` is not an instance of AFF4 stream.