Introduce a few smaller changes:
 -> Remove the 'getRegion' function for now. I can't determine the correct return type.
 -> Change the GQTError types. I've generalized them, while also clarifying what they actually indicate.
 -> Add the "envelopes" function.
 -> Introduce error handling to the "setRegion" function.
 -> Introduce error handling to the "deleteRegion" function.
 -> The remaining changes are simple minor tweaks/fixes/generalizations.