Importing

The structure for ListLib is as follows:

ListLib
    List
    NumList

To easily load all the modules, you can require the base ListLib module which returns a function to import the other two:

local import = require(ListLib)
local List, NumList = import("List", "NumList")

The importation will return the module functionality in the order of parameters.

Importing vs Requiring

It is highly recommended that you use the import function because it will initialize that script's environment with updated in-built functions such as pairs, type, typeof, etc. to recognize these datatypes and treat them accordingly. In scripts that you pass the objects as parameters, for example, and ListLib isn't be imported, the script environments will not be updated with these functions, so you must be the functions within the object itself such as List:Pairs and List.__type (for the above three).