Does anyone know how to change the key signature of a score?

My main goal is to change the key signature of a score using a plugin.
[the key signature is currently -1 (F Major), and I want to change it to -4 (F Minor)]

At first, I tried

cursor.score.keySig = 3;

but I realized after a while that cursor.score.keySig is read-only.

Afterwards, I tried removing the key signature using

removeElement(cursor.keySignature);

and

removeElement(cursor.score.keySig);

but I'm pretty sure that since both are read only, you can't use a plugin to remove them. (Which is probably why Musescore keeps crashing)