import argparse


def str2bool(v):
    if v is None:
        return None
    exclusive = ['accurate', 'query', 'document']
    if v in exclusive:
        return v
    if isinstance(v, bool):
        return v
    if v.lower() in ('yes', 'true', 't', 'y', '1'):
        return True
    elif v.lower() in ('no', 'false', 'f', 'n', '0'):
        return False
    else:
        raise argparse.ArgumentTypeError('Boolean value expected.')