Returns mzid spectra data filenames and their IDs used in the
    mzIdentML file as a dict. Keys == IDs, values == fns

def get_mzid_specfile_ids(mzidfn, namespace):
    """Returns mzid spectra data filenames and their IDs used in the
    mzIdentML file as a dict. Keys == IDs, values == fns"""
    sid_fn = {}
    for specdata in mzid_specdata_generator(mzidfn, namespace):
        sid_fn[specdata.attrib['id']] = specdata.attrib['name']
    return sid_fn