code: def strel_rectangle(width, height):
      
      return np.ones([int((hw - 1) // 2) * 2 + 1 for hw in (height, width)], bool)
docs: Create a rectangular structuring element
      
      width - the width of the structuring element (in the j direction). The
              width will be rounded down to the nearest multiple of 2*n+1
              
      height = the height of the structuring element (in the i direction). The
              height will be rounded down to the nearest multiple of 2*n+1