text: class Tree{
      constructor(leaf){
          this.leaf = leaf;
          this.lchild = undefined;
          this.rchild = undefined;
      }
  
      getLeafs(){
          if (this.lchild === undefined && this.rchild === undefined){
              return [this.leaf]
          } else {
              return [].concat(
                  this.lchild.getLeafs(),
                  this.rchild.getLeafs()
                  )
          }
      }
  
      getIncludedPoints(points){
          if (this.lchild === undefined && this.rchild === undefined){
              points.concat(this.leaf.getIncludedPoints(points));
          }
          if (this.lchild !== undefined){
              points.concat(this.lchild.getIncludedPoints(points));
          }
          if (this.rchild !== undefined){
              points.concat(this.rchild.getIncludedPoints(points));
          }
          // if there is an lchild and rchild, create and add points to
          // connect the two centers
          // if (this.lchild !== undefined && this.rchild !== undefined){
          //     points.concat(this.lchild.leaf.pointsBetweenCenters(points, this.rchild.leaf));
          // }
          return points
      }
  }