This is an example of a library. You may see a list of other libraries used on Rosetta Code at Category:Solutions by Library.
Wren-queue is a module which adds queue support to the Wren programming language. It consists of 3 classes: Queue, Deque and PriorityQueue. The first two of these represent single-ended and double-ended queues respectively. The last one represents a single-ended queue where each element has an associated priority.
It is the fifteenth in a series of modules (listed on the language's main page) designed to assist with writing Rosetta Code tasks so the same code does not have to be written or copy/pasted time and time again thereby bloating a task's script code unnecessarily.
To use it you all you need to do is to copy the source code (in the talk page) to a text file called queue.wren and place this in the same directory as the importing script so the command line interpreter can find it.