@Mostafa_El_Ayoubi is right, so in these cases you have to specify the reference assembly, namespace, class then the method. A good example is Plane.ByOriginNormal. To use in Python you have to declare the following otherwise it throws an exception:
pln = Autodesk.DesignScript.Geometry.Plane.ByOriginNormal( centreXYZ, Vector.ZAxis() )