code: def contains(self, key):
          "Exact matching."
          index = self.follow_bytes(key, self.ROOT)
          if index is None:
              return False
          return self.has_value(indexf contains(self, key):
          "Exact matching."
          index = self.follow_bytes(key, self.ROOT)
          if index is None:
              return False
          return self.has_value(index)
docs: Exact matching.