code: def _hyphenate(input, add_prefix=False):
      
      ret  = '--' if add_prefix else ''
      ret += input.replace('_', '-')
      return ret
docs: Change underscores to hyphens so that object attributes can be easily
      tranlated to GPG option names.
  
      :param str input: The attribute to hyphenate.
      :param bool add_prefix: If True, add leading hyphens to the input.
      :rtype: str
      :return: The ``input`` with underscores changed to hyphens.