def get_ext_file(raw_file):
    """Get file extension."""
    from nipype.utils.filemanip import split_filename as split_f
    subj_path, basename, ext = split_f(raw_file)
    print(raw_file)
    is_ds = False
    if ext == 'ds':
        is_ds = True
        return is_ds
    elif ext == 'fif':
        return is_ds
    else:
        raise RuntimeError('only fif and ds file format!!!')
