code: def stem(self, word):
          
          lowered = word.lower()
          if lowered[-3:] == 'ies' and lowered[-4:-3] not in {'e', 'a'}:
              return word[:-3] + ('Y' if word[-1:].isupper() else 'y')
          if lowered[-2:] == 'es' and lowered[-3:-2] not in {'a', 'e', 'o'}:
              return word[:-1]
          if lowered[-1:] == 's' and lowered[-2:-1] not in {'u', 's'}:
              return word[:-1]
          return word
docs: Return the S-stemmed form of a word.
  
          Parameters
          ----------
          word : str
              The word to stem
  
          Returns
          -------
          str
              Word stem
  
          Examples
          --------
          >>> stmr = SStemmer()
          >>> stmr.stem('summaries')
          'summary'
          >>> stmr.stem('summary')
          'summary'
          >>> stmr.stem('towers')
          'tower'
          >>> stmr.stem('reading')
          'reading'
          >>> stmr.stem('census')
          'census'