docs: def rmsd(self, other, backbone=False):
          """Calculates the RMSD between two AMPAL objects.
  
          Notes
          -----
          No fitting operation is performs and both AMPAL objects must
          have the same number of atoms.
  
          Parameters
          ----------
          other : AMPAL Object
              Any AMPAL object with `get_atoms` method.
          backbone : bool, optional
              Calculates RMSD of backbone only.
          """
          assert type(self) == type(other)
          if backbone and hasattr(self, 'backbone'):
              points1 = self.backbone.get_atoms()
              points2 = other.backbone.get_atoms()
          else:
              points1 = self.get_atoms()
              points2 = other.get_atoms()
          points1 = [x._vector for x in points1]
          points2 = [x._vector for x in points2]
          return rmsd(points1=points1, points2=points2)