code: def _get_nr_prefix(i):
      
      for lookup_range, prefix_string in _nr_prefix_strings.items():
          if i in lookup_range:
              return prefix_string
      raise ValueError("No prefix string associated with {0}!".format(i))
docs: Helper function for looking up the derived name prefix associated with a Unicode scalar value.
  
      :param i: Unicode scalar value.
      :return: String with the derived name prefix.