def test_empty_op_type(self):
        """
        If an op_type config is set to None. The entire class will not be compressed.
        """
        config = cto.coreml.OptimizationConfig(
            global_config=cto.coreml.OpPalettizerConfig(mode="kmeans", nbits=2),
            op_type_configs={
                "conv": None,
            },
        )
        compressor = quantization.palettize_weights(config=config)
        prog = self._get_test_program()
        compressor.apply(prog)
        expected_ops = [
            "conv",
            "reshape",
            "constexpr_lut_to_dense",
            "linear",
            "reshape",
            "constexpr_lut_to_dense",
            "conv_transpose",
        ]
        assert get_op_types_in_program(prog) == expected_ops
        conv_op = prog.find_ops(op_type="conv")[0]
        assert conv_op.weight.op.op_type == "const"

        If an op_type config is set to None. The entire class will not be compressed.
        
coremltools/test/optimize/coreml/test_passes.py