code: def hd(result, reference, voxelspacing=None, connectivity=1):
      
      hd1 = __surface_distances(result, reference, voxelspacing, connectivity).max()
      hd2 = __surface_distances(reference, result, voxelspacing, connectivity).max()
      hd = max(hd1, hd2)
      return hd
docs: Hausdorff Distance.
      
      Computes the (symmetric) Hausdorff Distance (HD) between the binary objects in two
      images. It is defined as the maximum surface distance between the objects.
      
      Parameters
      ----------
      result : array_like
          Input data containing objects. Can be any type but will be converted
          into binary: background where 0, object everywhere else.
      reference : array_like
          Input data containing objects. Can be any type but will be converted
          into binary: background where 0, object everywhere else.
      voxelspacing : float or sequence of floats, optional
          The voxelspacing in a distance unit i.e. spacing of elements
          along each dimension. If a sequence, must be of length equal to
          the input rank; if a single number, this is used for all axes. If
          not specified, a grid spacing of unity is implied.
      connectivity : int
          The neighbourhood/connectivity considered when determining the surface
          of the binary objects. This value is passed to
          `scipy.ndimage.morphology.generate_binary_structure` and should usually be :math:`> 1`.
          Note that the connectivity influences the result in the case of the Hausdorff distance.
          
      Returns
      -------
      hd : float
          The symmetric Hausdorff Distance between the object(s) in ```result``` and the
          object(s) in ```reference```. The distance unit is the same as for the spacing of 
          elements along each dimension, which is usually given in mm.
          
      See also
      --------
      :func:`assd`
      :func:`asd`
      
      Notes
      -----
      This is a real metric. The binary images can therefore be supplied in any order.