A do-nothing implementation of IClusteringAlgorithm. If no clusters are
provided from predecessor components, it produces an empty set of clusters. Otherwise
it just passes through the input cluster set.
ProcessingException - when processing failed. If thrown, the
IProcessingComponent.afterProcessing() method will be called and the component will
be ready to accept further requests or to be disposed of. Finally, the
exception will be rethrown from the controller method that caused the
component to perform processing.