title: Can not downsample a point cloud in open3D
body: <p>I am new to open3D pythong binding.</p>
  <p>I am trying to downsample a point clout and I have this code:</p>
  <pre><code>import open3d as o3d
  input_file='mypoints.ply'
  pcd = o3d.io.read_point_cloud(input_file)
  voxel_down_pcd = o3d.geometry.voxel_down_sample(pcd, voxel_size=0.02)
  o3d.visualization.draw_geometries([voxel_down_pcd])
  </code></pre>
  <p>but when I run the code I am getting this error:</p>
  <pre><code>module 'open3d.cpu.pybind.geometry' has no attribute 'voxel_down_sample'
  </code></pre>
  <p>I got the sample from Open3D website tutorial</p>
  <p>What is the problem and how I can fix it?</p>