code: def get_least_orbits(atom_index, cell, site_symmetry, symprec=1e-5):
      
      orbits = _get_orbits(atom_index, cell, site_symmetry, symprec)
      mapping = np.arange(cell.get_number_of_atoms())
  
      for i, orb in enumerate(orbits):
          for num in np.unique(orb):
              if mapping[num] > mapping[i]:
                  mapping[num] = mapping[i]
  
      return np.unique(mapping)
docs: Find least orbits for a centering atom