def demo_FixedSplines_addByNurbsCurve(sketch: adsk.fusion.Sketch):
# Define three points and create an arc along those points
pointOne = adsk.core.Point3D.create(0,0,0)
pointTwo = adsk.core.Point3D.create(6,9,0)
pointThree = adsk.core.Point3D.create(15,12,0)
arc3D = adsk.core.Arc3D.createByThreePoints(pointOne, pointTwo, pointThree)
nurbsCurve = arc3D.asNurbsCurve
# Create the spline using the 3D curve
splines = sketch.sketchCurves.sketchFixedSplines
fixedSpline = splines.addByNurbsCurve(nurbsCurve)