code: def strel_disk(radius):
      
      iradius = int(radius)
      x,y     = np.mgrid[-iradius:iradius+1,-iradius:iradius+1]
      radius2 = radius * radius
      strel   = np.zeros(x.shape)
      strel[x*x+y*y <= radius2] = 1
      return strel
docs: Create a disk structuring element for morphological operations
      
      radius - radius of the disk