Got it thanks~!
Glyphs.clearLog()
from GlyphsApp import GSPathPen
thisLayer = Font.selectedLayers[0]
layerPaths = [l for l in thisLayer.paths]
thisLayer.paths = []
for eachPath in layerPaths:
pen = GSPathPen.alloc().init()
eachPath.drawInPen_(pen)
eachPath = pen.layer().paths
eachPath = eachPath[0]
thisLayer.addPath_(eachPath)