Create a file header in the config.

    Args:
      fp: int, a file pointer for writing the header.

def _AddHeader(self, fp):
    """Create a file header in the config.

    Args:
      fp: int, a file pointer for writing the header.
    """
    text = textwrap.wrap(
        textwrap.dedent(self.config_header), break_on_hyphens=False)
    fp.write('\n'.join(['# ' + line for line in text]))
    fp.write('\n\n')