docs: def update_atom_numbers(self):
          """Update links "first_atom_number" -> "second_atom_number"
  
          :return: None.
          :rtype: :py:obj:`None`.
          """
          self._ctab_data['first_atom_number'] = self.first_atom.atom_number
          self._ctab_data['second_atom_number'] = self.second_atom.atom_number