@classmethod
def create(cls, server, option, value):
    """
        Based on the given option and value from the configuration
        file, creates the appropriate retention policy object
        for the given server
        """
    if option == 'wal_retention_policy':
        context = 'WAL'
    elif option == 'retention_policy':
        context = 'BASE'
    else:
        raise ValueError('Unknown option for retention policy: %s' % option)
    for policy_class in cls.policy_classes:
        policy = policy_class.create(server, context, value)
        if policy:
            return policy
    raise ValueError('Cannot parse option %s: %s' % (option, value))
