K_D树，python代码，对输入的三维点云数据(x,y,z)建立K_D，并返回前序遍历结果-K_D tree, Python code K_D establish three-dimensional point cloud data (x, y, z) input, and returns the result of the previous preorder

利用python语言构建三维的热力图模型，输入数据可以直接计算导出3D热力图(Using Python language to build three-dimensional thermodynamic chart model, input data can directly calculate the 3D thermal diagram.)