code: def tokenize(text):
  
      
  
      stem = PorterStemmer().stem
      tokens = re.finditer('[a-z]+', text.lower())
  
      for offset, match in enumerate(tokens):
  
          # Get the raw token.
          unstemmed = match.group(0)
  
          yield { # Emit the token.
              'stemmed':      stem(unstemmed),
              'unstemmed':    unstemmed,
              'offset':       offset
          }
docs: Yield tokens.
  
      Args:
          text (str): The original text.
  
      Yields:
          dict: The next token.