import vapoursynth as vs
core = vs.get_core()
clip = core.ffms2.Source(source="in1.mkv")

dst_fps_num = 60
dst_fps_den = 1

sup  = core.mv.Super(clip, pel=1, hpad=8, vpad=8) #see mvtools documentation
#create motion information, then interpolate frames
bvec = core.mv.Analyse(sup, blksize=4, isb=True , chroma=True, search=3, searchparam=1, truemotion=True)
fvec = core.mv.Analyse(sup, blksize=4, isb=False, chroma=True, search=3, searchparam=1, truemotion=True)
clip = core.mv.FlowFPS(clip, sup, bvec, fvec, num=dst_fps_num, den=dst_fps_den, thscd2=100)

clip.set_output()