@staticmethod
def _get_key_second_half(platform):
    """Get the key corresponding to the platform number.

        Returns:
             key_second_half(str): Representative submits tasks to several
                platforms.

        """
    setting_mappings = {'2': 'www2', '3': 'www3', '6': 'www6', '20': 'pic',
        '21': 'gpu'}
    return setting_mappings[platform]
