guideline.position normalization problem

[typesupply]

I think this is because _set_position uses moveBy to move the coordinates. moveBy calls transformBy which calls _transformBy. The guideline implementation of _transformBy doesn't normalize the resulting coordinates.

Demo:

from fontParts.fontshell import RGuideline

guideline = RGuideline()
guideline.position = (1, 2)
print(guideline.position)