How to use the fontmake.instantiator.swap_glyph_names function in fontmake

("public.kern1.aswap", "x"): 20,
        ("a", "y"): 40,
        ("a.swap", "y"): 30,
        ("y", "a"): 60,
        ("y", "a.swap"): 50,
    }

    # Test swapped group membership.
    assert ufo.groups == {
        "public.kern1.a": ["a.swap"],
        "public.kern1.aswap": ["a"],
        "public.kern2.a": ["a.swap", "a"],
    }

    # Swap a second time.
    fontmake.instantiator.swap_glyph_names(ufo, "aaa", "aaa.swap")

    # Test swapped glyphs.
    assert sorted(c.baseGlyph for c in ufo["aaa"].components) == ["a", "a", "y"]
    assert sorted(c.baseGlyph for c in ufo["aaa.swap"].components) == [
        "a.swap",
        "a.swap",
        "x",
    ]

    # Test for no leftover temporary glyphs.
    assert {g.name for g in ufo} == {
        "space",
        "a",
        "a.swap",
        "aaa",
        "aaa.swap",

def test_swap_glyph_names_spec(data_dir):
    """Test that the rule example in the designspaceLib spec works.

    `adieresis` should look the same as before the rule application.

    [1]: https://github.com/fonttools/fonttools/tree/master/Doc/source/designspaceLib#ufo-instances
    """
    ufo = ufoLib2.Font.open(data_dir / "SwapGlyphNames" / "B.ufo")
    fontmake.instantiator.swap_glyph_names(ufo, "a", "a.alt")

    assert sorted(c.baseGlyph for c in ufo["adieresis"].components) == [
        "a.alt",
        "dieresiscomb",
    ]
    assert sorted(c.baseGlyph for c in ufo["adieresis.alt"].components) == [
        "a",
        "dieresiscomb",
    ]

def test_swap_glyph_names(data_dir):
    ufo = ufoLib2.Font.open(data_dir / "SwapGlyphNames" / "A.ufo")

    fontmake.instantiator.swap_glyph_names(ufo, "a", "a.swap")

    # Test swapped outlines.
    assert ufo["a"].unicode == 0x61
    assert len(ufo["a"]) == 1
    assert len(ufo["a"].contours[0]) == 8
    assert ufo["a"].width == 666
    assert ufo["a.swap"].unicode is None
    assert len(ufo["a.swap"]) == 1
    assert len(ufo["a.swap"].contours[0]) == 4
    assert ufo["a.swap"].width == 600

    # Test swapped components.
    assert sorted(c.baseGlyph for c in ufo["aaa"].components) == [
        "a.swap",
        "a.swap",
        "x",

"x",
    ]

    # Test for no leftover temporary glyphs.
    assert {g.name for g in ufo} == {
        "space",
        "a",
        "a.swap",
        "aaa",
        "aaa.swap",
        "x",
        "y",
    }

    with pytest.raises(fontmake.instantiator.InstantiatorError, match="Cannot swap"):
        fontmake.instantiator.swap_glyph_names(ufo, "aaa", "aaa.swapa")