def METHOD_NAME():
    a = ak.contents.indexedarray.IndexedArray(
        ak.index.Index(np.array([5, 4, 3, 2, 1, 0], np.int64)),
        ak.contents.numpyarray.NumpyArray(np.array([1.1, 2.2, 3.3, 4.4, 5.5, 6.6])),
    )
    b = ak.contents.indexedarray.IndexedArray(
        ak.index.Index(np.array([0, 1, 2], np.int64)),
        ak.contents.numpyarray.NumpyArray(np.array([7.7, 8.8, 9.9])),
    )
    c = ak.concatenate([a, b])
    ctt = ak.concatenate([a.to_typetracer(), b.to_typetracer()])
    assert c.to_list() == [6.6, 5.5, 4.4, 3.3, 2.2, 1.1, 7.7, 8.8, 9.9]
    assert isinstance(c.layout, ak.contents.IndexedArray)
    assert c.layout.form == IndexedForm("i64", NumpyForm("float64"))
    assert c.layout.form == ctt.layout.form