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

def test_interpolation(data_dir):
    designspace = designspaceLib.DesignSpaceDocument.fromfile(
        data_dir / "DesignspaceTest" / "DesignspaceTest.designspace"
    )
    generator = fontmake.instantiator.Instantiator.from_designspace(
        designspace, round_geometry=True
    )

    instance_font = generator.generate_instance(designspace.instances[0])
    assert instance_font["l"].width == 220

def test_interpolation_weight_width_class(data_dir):
    designspace = designspaceLib.DesignSpaceDocument.fromfile(
        data_dir / "MutatorSans" / "MutatorSans.designspace"
    )
    generator = fontmake.instantiator.Instantiator.from_designspace(
        designspace, round_geometry=True
    )

    for instance in designspace.instances:
        instance.font = generator.generate_instance(instance)

    # LightCondensed
    font = designspace.instances[0].font
    assert font.info.openTypeOS2WeightClass == 1
    assert font.info.openTypeOS2WidthClass == 1

    # BoldCondensed
    font = designspace.instances[1].font
    assert font.info.openTypeOS2WeightClass == 1000
    assert font.info.openTypeOS2WidthClass == 1

include()s and writes the resulting full feature file to all instance
                UFOs. Use this if you share feature files among masters in external
                files. Otherwise, the relative include paths can break as instances
                may end up elsewhere. Only done on interpolation.
        Returns:
            generator of ufoLib2.Font objects corresponding to the UFO instances.
        Raises:
            ValueError: The Designspace has no default source or contains incompatible
                glyphs or contains anisotropic (MutatorMath) locations or contains a
                 substitution for a non-existant glyph.
        """
        from glyphsLib.interpolation import apply_instance_data_to_ufo

        logger.info("Interpolating master UFOs from designspace")
        designspace = designspaceLib.DesignSpaceDocument.fromfile(designspace.path)
        generator = instantiator.Instantiator.from_designspace(
            designspace, round_geometry=round_instances
        )

        if expand_features_to_instances:
            logger.debug("Expanding features to instance UFOs")
            fea_txt = parseLayoutFeatures(designspace.default.font).asFea()
            generator = attr.evolve(generator, copy_feature_text=fea_txt)

        for instance in designspace.instances:
            # Skip instances that have been set to non-export in Glyphs, stored as the
            # instance's `com.schriftgestaltung.export` lib key.
            if not instance.lib.get("com.schriftgestaltung.export", True):
                continue

            # Skip instances that do not match the user's inclusion regex if given.
            if include is not None and not fullmatch(include, instance.name):