VS crashing script

import vapoursynth as vs
import sys

core = vs.Core()
core.std.LoadPlugin(path=r'C:\Program Files\Media\VapourSynth\plugins\ffms2.dll')
# core.avs.LoadPlugin(path=r'c:\avisynth\UnDot.dll')

ret = core.ffms2.Source(source=r"T:\incoming\KaranAnime\The World God Only Knows\[Chihiro]_The_World_God_Only_Knows_-_01_[1280x720_H.264_AAC][397A7B12].mkv")
print(ret)
ret.output(sys.stdout, y4m=True)