The PSE will run any code you give it and will run it in it's own sandbox environment. What this means is that code will run with absolutely no functions or variables except for what you give it.
This means, unless you say so, the PSE will run code without any of the lua standard functions. However, any code the PSE runs cannot affect anything other than the functions and variables you give it.
I named my function by putting an underscore in between words, however, I also provided functions named in camel case that do the same thing. For example: new_sandbox() and newSandbox()