def METHOD_NAME():
    defs = session.evaluation.definitions
    instance_custom_atom = CustomAtom(expression=False)
    instance_custom_atom.contribute(defs, is_pymodule=True)
    evaluate("MakeBoxes[CustomAtom, InputForm]")
    formatted = session.format_result().boxes_to_mathml()
    assert formatted == "CustomBoxExpression<<[1, 2, 3]>>"