@staticmethod
def _add_nullbytes(buffer_str):
    """
        Adds nullbits between letters.

        :param buffer_str:
        :return: string with nullbits

        >>> McdParserBase._add_nullbytes('abc')
        'a\\x00b\\x00c\\x00'
        """
    pad_str = ''
    for s in buffer_str:
        pad_str += s + '\x00'
    return pad_str
