docs: protected QuadTree findIndex(INDArray coordinates) {
  
          // Compute the sector for the coordinates
          boolean left = (coordinates.getDouble(0) <= (boundary.getX() + boundary.getHw() / 2));
          boolean top = (coordinates.getDouble(1) <= (boundary.getY() + boundary.getHh() / 2));
  
          // top left
          QuadTree index = getNorthWest();
          if (left) {
              // left side
              if (!top) {
                  // bottom left
                  index = getSouthWest();
              }
          } else {
              // right side
              if (top) {
                  // top right
                  index = getNorthEast();
              } else {
                  // bottom right
                  index = getSouthEast();
  
              }
          }
  
          return index;
      }