How to use the pdal.pio.PipelineSpec function in pdal

def test_pipeline_construction(self):
        pipeline = (pio.readers.ply(filename="dummyinput.ply") +
                    pio.filters.outlier(method="statistical", mean_k=16, multiplier=1.0) +
                    pio.filters.range(limits="Classification![7:7]") +
                    pio.filters.normal() + pio.writers.ply(storage_mode="ascii", precision=4, filename="dummyoutput.ply",
                                                           dims="X,Y,Z,Red,Green,Blue,NormalX,NormalY,NormalZ"))

        self.assertIsInstance(pipeline, pio.PipelineSpec)
        self.assertEqual(len(list(pipeline.stages)), 5)
        self.assertEqual(json.dumps(pipeline.spec, indent=2), dummy_pipeline)

        auto_reader = pio.readers.auto(filename="dummyinput.las")
        auto_writer = pio.writers.auto(filename="dummyoutput.las")

        self.assertIn("filename", auto_reader.spec)
        self.assertNotIn("type", auto_reader.spec)
        self.assertIn("filename", auto_reader.spec)
        self.assertNotIn("type", auto_writer.spec)
        self.assertEqual(auto_reader.prefix, "readers")
        self.assertEqual(auto_writer.prefix, "writers")

def pipeline(self):
        """
        Promote this stage to  a `pdal.pio.PipelineSpec` with one `pdal.pio.StageSpec`
        and return it.
        """
        output = PipelineSpec()
        output.add_stage(self)
        return output

def __add__(self, stage_or_pipeline):
        assert isinstance(stage_or_pipeline, (StageSpec, PipelineSpec)), "Expected StageSpec or PipelineSpec"

        output = self.__class__(self)
        if isinstance(stage_or_pipeline, StageSpec):
            output.add_stage(stage_or_pipeline)
        elif isinstance(stage_or_pipeline, PipelineSpec):
            for stage in stage_or_pipeline.stages:
                output.add_stage(stage)
        return output

def __add__(self, stage_or_pipeline):
        assert isinstance(stage_or_pipeline, (StageSpec, PipelineSpec)), "Expected StageSpec or PipelineSpec"

        output = self.__class__(self)
        if isinstance(stage_or_pipeline, StageSpec):
            output.add_stage(stage_or_pipeline)
        elif isinstance(stage_or_pipeline, PipelineSpec):
            for stage in stage_or_pipeline.stages:
                output.add_stage(stage)
        return output