code: def fit_rmsd(ras, rbs, weights=None):
      
      transformation = superpose(ras, rbs, weights)
      rbs_trans = transformation * rbs
      rmsd = compute_rmsd(ras, rbs_trans)
      return transformation, rbs_trans, rmsd
docs: Fit geometry rbs onto ras, returns more info than superpose
  
         Arguments:
          | ``ras``  --  a numpy array with 3D coordinates of geometry A,
                         shape=(N,3)
          | ``rbs``  --  a numpy array with 3D coordinates of geometry B,
                         shape=(N,3)
  
         Optional arguments:
          | ``weights``  --  a numpy array with fitting weights for each
                             coordinate, shape=(N,)
  
         Return values:
          | ``transformation``  --  the transformation that brings geometry A into
                                    overlap with geometry B
          | ``rbs_trans``  --  the transformed coordinates of geometry B
          | ``rmsd``  --  the rmsd of the distances between corresponding atoms in
                          geometry A and B
  
         This is a utility routine based on the function superpose. It just
         computes rbs_trans and rmsd after calling superpose with the same
         arguments