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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def untargz(input_targz_file, untar_to_dir):
 """ This module accepts a tar.gz archive and untars it. RETURN VALUE: path to the untar-ed directory/file NOTE: this module expects the multiple files to be in a directory before being tar-ed. """

    assert tarfile.is_tarfile(input_targz_file), 'Not a tar file.'
    tarball = tarfile.open(input_targz_file)
    return_value = os.path.join(untar_to_dir, tarball.getmembers()[0].name)
    tarball.extractall(path=untar_to_dir)
    tarball.close()
    return return_value