Changed PipelineModel(...) to self.cls(...) in pyspark.ml.pipeline.PipelineModelReader.load()

CustomPipelineModel(PipelineModel):
    def _transform(self, df):
        ...
 CustomPipelineModel.save('path/to/file') # works
 CustomPipelineModel.load('path/to/file') # wrong: results in PipelineModel() instead of CustomPipelineModel()
 CustomPipelineModel.transform() # wrong: results in calling PipelineModel.transform() instead of CustomPipelineModel.transform()