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An abstract QgsProcessingAlgorithm base class for processing algorithms which operate "feature-by-feature". Feature based algorithms are algorithms which operate on individual features in isolation. These are algorithms where one feature is output for each input feature, and the output feature result for each input feature is not dependent on any other features present in the source. For instance, algorithms like "centroids" and "buffers" are feature based algorithms since the centroid or buffer of a feature is calculated for each feature in isolation. An algorithm like "dissolve" is NOT suitable for a feature based algorithm as the dissolved output depends on multiple input features and these features cannot be processed in isolation. Using QgsProcessingFeatureBasedAlgorithm as the base class for feature based algorithms allows shortcutting much of the common algorithm code for handling iterating over sources and pushing features to output sinks. It also allows the algorithm execution to be optimised in future (for instance allowing automatic multi-thread processing of the algorithm, or use of the algorithm in "chains", avoiding the need for temporary outputs in multi-step models).