docs: def add(self, iterable):
          """ Insert an iterable (pattern) item into the markov chain.
              The order of the pattern will define more of the chain.
          """
          item1 = item2 = MarkovChain.START
          for item3 in iterable:
              self[(item1, item2)].add_side(item3)
              item1 = item2
              item2 = item3
          self[(item1, item2)].add_side(MarkovChain.END)