API: PythonOCC and FreeCAD are incompatible when imported into the same python File


When I import FreeCAD and Part module, I also import some module in OCC.Core. But, I got some errors listed below.
"ImportError: /OCC/Core/_STEPControl.so: undefined symbol: "

However, if I only import one of them,(e.t. only import OCC or only import FreeCAD), I won't got the above errors.
So, can any one help to explain it, and how to solve it. Thanks a lot.