docs: private void initVariables() {
          if (this.currentChunk == null) {
              this.currentChunk = new Instances(this.getModelContext());
          }
  
          if (this.classDistributions == null) {
              this.classDistributions = new long[this.getModelContext().classAttribute().numValues()];
  
              for (int i = 0; i < this.classDistributions.length; i++) {
                  this.classDistributions[i] = 0;
              }
          }
      }