docs: @Override
      public void merge(ROCMultiClass other) {
          if (this.underlying == null) {
              this.underlying = other.underlying;
              return;
          } else if (other.underlying == null) {
              return;
          }
  
          //Both have data
          if (underlying.length != other.underlying.length) {
              throw new UnsupportedOperationException("Cannot merge ROCBinary: this expects " + underlying.length
                              + "outputs, other expects " + other.underlying.length + " outputs");
          }
          for (int i = 0; i < underlying.length; i++) {
              this.underlying[i].merge(other.underlying[i]);
          }
      }