def get_parser():
    """Build parser object"""
    from argparse import ArgumentParser
    from argparse import RawTextHelpFormatter
    parser = ArgumentParser(description=
        "OpenfMRI participants sampler, for FMRIPREP's testing purposes",
        formatter_class=RawTextHelpFormatter)
    parser.add_argument('openfmri_dir', action='store', help=
        'the root folder of a the openfmri dataset')
    parser.add_argument('-D', '--datalad_fetch', action='store_true',
        default=False, help='download sampled subjects')
    parser.add_argument('-o', '--output-file', action='store', help=
        'write output file')
    parser.add_argument('-n', '--num-participants', action='store', type=
        int, default=4, help=
        'number of participants randomly selected per dataset')
    parser.add_argument('--njobs', action='store', type=int, help=
        'parallel downloads')
    parser.add_argument('--seed', action='store', type=int, default=
        20170914, help='seed for random number generation')
    return parser
