This is not an actual Lua module. It exists to provide a convenient pseudo-namespace for code testing, hopefully preventing the main Module: namespace from becoming littered with experiments, as Lua modules cannot exist as subpages in the User: namespace.
Please name your experimental modules in the following format to help keep things tidy:
Module:Sandbox/Your User Name
You can use Special:PrefixIndex/Module:Sandbox to list modules in this area.