new_contents: #!/usr/bin/env python
  
  from numpy import all, allclose, array, float32
  
  from .. import filter
  
  
  x = array([
      [0, 1, 0],
      [1, 1, 1],
      [0, 1, 0],
  ], dtype=float32)
  
  
  def test_low_pass_filter():
      y = filter._low_pass_filter(x.shape, 1)
      assert all(x == y)
      z = filter._high_pass_filter(x.shape, 1)
      assert all(z == 1.0 - y)
  
  
  def test_lowpass():
      y = filter._lowpass(3, x)
      assert allclose(x, y)
  
  
  if __name__ == '__main__':
      pass
  
subject: Add unit tests for the filter module.