code: def test_median_filter():
      A = np.zeros((128, 128), bool)
      A[3::3, 3::3] = 1
      Am = median_filter(A)
      assert not Am.any()
      assert Am.shape == A.shape
  
file_path: mahotas/mahotas/tests/test_median_filter.py
imports: import numpy
  from mahotas.convolve import median_filter, rank_filter
  import pytest
label_desc: Use image node_id 1 for calling a global function with example usage: test_median_filter() without return types