def consolidate_tarballs_job(job, fname_to_id):
    """
    Combine the contents of separate tarballs into one.
    Subdirs within the tarball will be named the keys in **fname_to_id

    :param JobFunctionWrappingJob job: passed automatically by Toil
    :param dict[str,str] fname_to_id: Dictionary of the form: file-name-prefix=FileStoreID
    :return: The file store ID of the generated tarball
    :rtype: str
    """
    work_dir = job.fileStore.getLocalTempDir()
    # Retrieve output file paths to consolidate
    tar_paths = []
    for fname, file_store_id in fname_to_id.iteritems():
        p = job.fileStore.readGlobalFile(file_store_id, os.path.join(work_dir, fname + '.tar.gz'))
        tar_paths.append((p, fname))
    # I/O
    # output_name is arbitrary as this job function returns a FileStoreId
    output_name = 'foo.tar.gz'
    out_tar = os.path.join(work_dir, output_name)
    # Consolidate separate tarballs into one
    with tarfile.open(os.path.join(work_dir, out_tar), 'w:gz') as f_out:
        for tar, fname in tar_paths:
            with tarfile.open(tar, 'r') as f_in:
                for tarinfo in f_in:
                    with closing(f_in.extractfile(tarinfo)) as f_in_file:
                        tarinfo.name = os.path.join(output_name, fname, os.path.basename(tarinfo.name))
                        f_out.addfile(tarinfo, fileobj=f_in_file)
    return job.fileStore.writeGlobalFile(out_tar)
Combine the contents of separate tarballs into one.
    Subdirs within the tarball will be named the keys in **fname_to_id

    :param JobFunctionWrappingJob job: passed automatically by Toil
    :param dict[str,str] fname_to_id: Dictionary of the form: file-name-prefix=FileStoreID
    :return: The file store ID of the generated tarball
    :rtype: str