docs: def search(self, key, default=None):
          """Find the first key-value pair with key *key* and return its value.
  
          If the key was not found, return *default*. If no default was provided,
          return ``None``. This method never raises a ``KeyError``.
          """
          self._find_lt(key)
          node = self._path[0][2]
          if node is self._tail or key < node[0]:
              return default
          return node[1]