code: def get_miller_index_from_site_indexes(self, site_ids, round_dp=4,
                                             verbose=True):
          
          return self.lattice.get_miller_index_from_coords(
              self.frac_coords[site_ids], coords_are_cartesian=False,
              round_dp=round_dp, verbose=verbose)
docs: Get the Miller index of a plane from a set of sites indexes.
  
          A minimum of 3 sites are required. If more than 3 sites are given
          the best plane that minimises the distance to all points will be
          calculated.
  
          Args:
              site_ids (list of int): A list of site indexes to consider. A
                  minimum of three site indexes are required. If more than three
                  sites are provided, the best plane that minimises the distance
                  to all sites will be calculated.
              round_dp (int, optional): The number of decimal places to round the
                  miller index to.
              verbose (bool, optional): Whether to print warnings.
  
          Returns:
              (tuple): The Miller index.