Public arg validation

[JoeZiminski]

Add initial validation for all public function arguments. There are better ways to do this, and key improvements in a soon-to-come issue will be:

1. move up as many low-level assert checks into exceptions that raise as soon as the fucntions are run. This will help avoid mid-pipeline crashes and also clean up the code
2. Use a proper validator package similar to Niko's work on movement.