code: def append(self, word, lemma=None, type=None, chunk=None, role=None, relation=None, pnp=None, anchor=None, iob=None, custom={}):
          
          self._do_word(word, lemma, type)            # Append Word object.
          self._do_chunk(chunk, role, relation, iob)  # Append Chunk, or add last word to last chunk.
          self._do_conjunction()
          self._do_relation()
          self._do_pnp(pnp, anchor)
          self._do_anchor(anchor)
          self._do_custom(custom)
docs: Appends the next word to the sentence / chunk / preposition.
              For example: Sentence.append("clawed", "claw", "VB", "VP", role=None, relation=1)
              - word     : the current word,
              - lemma    : the canonical form of the word,
              - type     : part-of-speech tag for the word (NN, JJ, ...),
              - chunk    : part-of-speech tag for the chunk this word is part of (NP, VP, ...),
              - role     : the chunk's grammatical role (SBJ, OBJ, ...),
              - relation : an id shared by other related chunks (e.g., SBJ-1 <=> VP-1),
              - pnp      : PNP if this word is in a prepositional noun phrase (B- prefix optional),
              - iob      : BEGIN if the word marks the start of a new chunk,
                           INSIDE (optional) if the word is part of the previous chunk,
              - custom   : a dictionary of (tag, value)-items for user-defined word tags.