This API is currently available in C++ and Python.
bool OESubsetDesignUnit(OEDesignUnit &du, const OEDesignUnit &refDu, const unsigned componentMask)
This function generates a fully-functional OEDesignUnit object (du) as subset of another OEDesignUnit (refDu) object. An additional bit mask (componentMask) is required to specify which components should be extracted as the subset. The bit mask should be specified from constants in the OEDesignUnitComponents namespace.