Refactoring pipeline concept #2: Got rid of distinguishing between AbstractPipeline and VisualizationPipeline. Every AbstractPipeline is also a VisualizationPipeline. However, AbstractPipeline does not care about evaluating its components - this has to be implemented in its subclasses.
AutoEvaluationPipeline subclasses AbstractPipeline and automatically evaluates the pipeline by listening to the signals of its components and calling the corresponding process() methods.