function mapSet(key, value) {
	      if (key != '__proto__') {
	        this.__data__[key] = value;
	      }
	      return this;
	    }
Sets `value` to `key` of the cache.

@private
@name set
@memberOf _.memoize.Cache
@param {string} key The key of the value to cache.
@param {*} value The value to cache.
@returns {Object} Returns the cache object.