code: def chunked(sentence):
      
      # For example, to construct a training vector with the head of previous chunks as a feature.
      # Doing this with Sentence.chunks would discard the punctuation marks and conjunctions
      # (Sentence.chunks only yields Chunk objects), which amy be useful features.
      chunks = []
      for word in sentence:
          if word.chunk is not None:
              if len(chunks) == 0 or chunks[-1] != word.chunk:
                  chunks.append(word.chunk)
          else:
              ch = Chink(sentence)
              ch.append(word.copy(ch))
              chunks.append(ch)
      return chunks
docs: Returns a list of Chunk and Chink objects from the given sentence.
          Chink is a subclass of Chunk used for words that have Word.chunk == None
          (e.g., punctuation marks, conjunctions).