def METHOD_NAME(xray_structure):
  asu_mappings = xray_structure.asu_mappings(buffer_thickness=3.5)
  pair_asu_table = crystal.pair_asu_table(asu_mappings=asu_mappings)
  scattering_types = xray_structure.scatterers().extract_scattering_types()
  pair_asu_table.add_covalent_pairs(
    scattering_types, exclude_scattering_types=flex.std_string(("H","D")))
  return pair_asu_table.extract_pair_sym_table()