docs: @Override
      protected void invokePreStepArtifacts() {
  
          if (stepListeners != null) {
              for (StepListenerProxy listenerProxy : stepListeners) {
                  // Call beforeStep on all the step listeners
                  listenerProxy.beforeStep();
              }
          }
  
          // Invoke the reducer before all parallel steps start (must occur
          // before mapper as well)
          if (this.partitionReducerProxy != null) {
              this.partitionReducerProxy.beginPartitionedStep();
          }
      }