Error check
    :rtype : object

def error_check(options):
    """
    Error check
    :rtype : object
    """

    compare = options.compare
    ensemble_paths = options.ensemble_paths

    if compare and len(ensemble_paths) > 2:
        print("\n Only 2 ensembles can be compared, {d} were specified\n".format(d=len(ensemble_paths)))
        sys.exit(1)