Validate the beacon configuration

def validate(config):
    '''
    Validate the beacon configuration
    '''
    if not isinstance(config, list):
        return False, ('Configuration for telegram_bot_msg '
                       'beacon must be a list.')

    _config = {}
    list(map(_config.update, config))

    if not all(_config.get(required_config)
               for required_config in ['token', 'accept_from']):
        return False, ('Not all required configuration for '
                       'telegram_bot_msg are set.')

    if not isinstance(_config.get('accept_from'), list):
        return False, ('Configuration for telegram_bot_msg, '
                       'accept_from must be a list of usernames.')

    return True, 'Valid beacon configuration.'