code: def demo():
      """
      A demonstration of the porter stemmer on a sample from
      the Penn Treebank corpus.
      """
  
      from nltk import stem
      from nltk.corpus import treebank
  
      stemmer = stem.PorterStemmer()
  
      orig = []
      stemmed = []
      for item in treebank.fileids()[:3]:
          for word, tag in treebank.tagged_words(item):
              orig.append(word)
              stemmed.append(stemmer.stem(word))
  
      # Convert the results to a string, and word-wrap them.
      results = " ".join(stemmed)
      results = re.sub(r"(.{,70})\s", r"\1\n", results + " ").rstrip()
  
      # Convert the original to a string, and word wrap it.
      original = " ".join(orig)
      original = re.sub(r"(.{,70})\s", r"\1\n", original + " ").rstrip()
  
      # Print the results.
      print("-Original-".center(70).replace(" ", "*").replace("-", " "))
      print(original)
      print("-Results-".center(70).replace(" ", "*").replace("-", " "))
      print(results)
      print("*" * 70)
  
imports: import re
  from nltk.stem.api import StemmerI
label_desc: Use image node_id 1 for calling a global function with example usage: demo() without return types