@staticmethod
def _camel2underline(s):
    """
            convert variables camel2underline
        """
    s = list(s)
    for index, value in enumerate(s[1:]):
        if 'A' <= value <= 'Z':
            s[index + 1] = '_' + value.lower()
    return ''.join(s).lower().replace('-', '_')
