code: function stackSet(key, value) {
      var cache = this.__data__;
      if (cache instanceof ListCache) {
        var pairs = cache.__data__;
        if (!Map || (pairs.length < LARGE_ARRAY_SIZE - 1)) {
          pairs.push([key, value]);
          return this;
        }
        cache = this.__data__ = new MapCache(pairs);
      }
      cache.set(key, value);
      return this;
    }
docs: Sets the stack `key` to `value`.
  
  @private
  @name set
  @memberOf Stack
  @param {string} key The key of the value to set.
  @param {*} value The value to set.
  @returns {Object} Returns the stack cache instance.