code: def lookup(self, prefix, lo=0, hi=None):
          
          words = self.words
          if hi is None: hi = len(words)
          i = bisect.bisect_left(words, prefix, lo, hi)
          if i < len(words) and words[i].startswith(prefix):
              return i, (words[i] == prefix)
          else:
              return None, False
docs: See if prefix is in dictionary, as a full word or as a prefix.
          Return two values: the first is the lowest i such that
          words[i].startswith(prefix), or is None; the second is
          True iff prefix itself is in the Wordlist.