new_contents: import unittest
  import pcl
  from patty.conversions.conversions import loadLas, writeLas
  import numpy as np
  
  class TestVoxelFilter(unittest.TestCase):
      def testFilter162(self):
          pc = loadLas('data/footprints/162.las')
          vgf = pc.make_voxel_grid_filter()
          vgf.set_leaf_size(1, 1, 1)
  
          pc2 = vgf.filter()
          pc2.offset = pc.offset
          writeLas('data/footprints/162_sparse.las', pc2)
  
  
subject: Add voxel filtering test