new_contents: import pymorph
  import numpy as np 
  
  def test_cwatershed():
      S = np.array([
          [0,0,0,0],
          [0,1,2,1],
          [1,1,1,1],
          [0,0,1,0],
          [1,1,1,1],
          [1,2,2,1],
          [1,1,2,2]
          ])
      M = np.array([
          [0,0,0,0],
          [0,0,1,0],
          [0,0,0,0],
          [0,0,0,0],
          [0,0,0,0],
          [0,2,0,0],
          [0,0,0,0],
          ])
      W = pymorph.cwatershed(2-S,M)
      assert np.all(W ==
       np.array([[1, 1, 1, 1],
                 [1, 1, 1, 1],
                 [1, 1, 1, 1],
                 [2, 2, 1, 1],
                 [2, 2, 2, 2],
                 [2, 2, 2, 2],
                 [2, 2, 2, 2]]))
  
  def test_watershed():
      S = np.array([
          [0,0,0,0],
          [0,1,2,1],
          [1,1,1,1],
          [0,0,1,0],
          [1,1,1,1],
          [1,2,2,1],
          [1,1,2,2]
          ])
      W = pymorph.watershed(2-S)
      assert np.all(W ==
       np.array([[1, 1, 1, 1],
                 [1, 1, 1, 1],
                 [1, 1, 1, 1],
                 [2, 2, 1, 1],
                 [2, 2, 2, 2],
                 [2, 2, 2, 2],
                 [2, 2, 2, 2]]))
  
subject: Test (c)watershed