[PyQt] How can I export a utility function using SIP?

[Frost Ming]

I am working on exporting the API from C++ to python to test Qt GUI.
In the .sip file, I use fake class definition. Symbols definitions are got from GUI after it is launched so I don't have to export all the dependent libraries. But it doesn't work for utility functions which does not rely on any classes.  Exporting flow are successful but when import the exported module, it says cannot find symbols definition.
Here is what the sip file like:

// not a module, must be included in another sip file
// Utility funtions to handle chartplot object
namespace lib {
namespace infra {
namespace chartplot {

// Lines between %TypeHeaderCode...%End are Fake definitions.
%TypeHeaderCode
namespace lib {
namespace infra {
namespace chartplot {
class ChartPanelBase;
int getXCoor(lib::infra::chartplot::ChartPanelBase* chartPanel, double v);
int getYCoor(lib::infra::chartplot::ChartPanelBase* chartPanel, double v);
double getXValue(lib::infra::chartplot::ChartPanelBase* chartPanel, int xCoor);
double getYValue(lib::infra::chartplot::ChartPanelBase* chartPanel, int yCoor);

} // namespace chartplot
} // namespace infra
} // namespace lib
%End

int getXCoor(lib::infra::chartplot::ChartPanelBase* chartPanel, double v);
int getYCoor(lib::infra::chartplot::ChartPanelBase* chartPanel, double v);
double getXValue(lib::infra::chartplot::ChartPanelBase* chartPanel, int xCoor);
double getYValue(lib::infra::chartplot::ChartPanelBase* chartPanel, int yCoor);

}; // namespace chartplot
}; // namespace infra
}; // namespace lib


Any help?

Best Regards,
Frost Ming

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