code: def get_contours(data, levels):
      
      if not have_skimage:
          raise Exception("Please install scikit-image > 0.13"
                          "to use this function")
      res = [filter(lambda arr: len(arr) >= 3,
                    measure.find_contours(data, level))
             for level in levels]
      res = [map(lambda arr: np.roll(arr, 1, axis=1),
                 arrs) for arrs in res]
      return res
docs: Get sets of contour points for numpy array `data`.
      `levels` is a sequence of values around which to calculate the
      contours.  Returns a list of numpy arrays of points--each array
      makes a polygon if plotted as such.