code: def _sb_r1(self, term, r1_prefixes=None):
          
          vowel_found = False
          if hasattr(r1_prefixes, '__iter__'):
              for prefix in r1_prefixes:
                  if term[: len(prefix)] == prefix:
                      return len(prefix)
  
          for i in range(len(term)):
              if not vowel_found and term[i] in self._vowels:
                  vowel_found = True
              elif vowel_found and term[i] not in self._vowels:
                  return i + 1
          return len(term)
docs: Return the R1 region, as defined in the Porter2 specification.
  
          Parameters
          ----------
          term : str
              The term to examine
          r1_prefixes : set
              Prefixes to consider
  
          Returns
          -------
          int
              Length of the R1 region