code: def dilation(x, radius=3):
      
      mask = disk(radius)
      x = dilation(x, selem=mask)
  
      return x
docs: Return greyscale morphological dilation of an image,
      see `skimage.morphology.dilation <http://scikit-image.org/docs/dev/api/skimage.morphology.html#skimage.morphology.dilation>`__.
  
      Parameters
      -----------
      x : 2D array
          An greyscale image.
      radius : int
          For the radius of mask.
  
      Returns
      -------
      numpy.array
          A processed greyscale image.