function cachePush(value) {
	  var map = this.__data__;
	  if (isKeyable(value)) {
	    var data = map.__data__,
	        hash = typeof value == 'string' ? data.string : data.hash;

	    hash[value] = HASH_UNDEFINED;
	  }
	  else {
	    map.set(value, HASH_UNDEFINED);
	  }
	}
Adds `value` to the set cache.

@private
@name push
@memberOf SetCache
@param {*} value The value to cache.