def ParseBool(text):
    """Parse a boolean value.

  Args:
    text: Text to parse.

  Returns:
    Boolean values parsed

  Raises:
    ValueError: If text is not a valid boolean.
  """
    if text in ('true', 't', '1'):
        return True
    elif text in ('false', 'f', '0'):
        return False
    else:
        raise ValueError('Expected "true" or "false".')
