Sets the list cache `key` to `value`.

@private
@name set
@memberOf ListCache
@param {string} key The key of the value to set.
@param {*} value The value to set.
@returns {Object} Returns the list cache instance.
function listCacheSet$3(key, value) {
	  var data = this.__data__,
	      index = _assocIndexOf(data, key);

	  if (index < 0) {
	    ++this.size;
	    data.push([key, value]);
	  } else {
	    data[index][1] = value;
	  }
	  return this;
	}