Simulink Embedded Coder: Export init/entry/step function into a seprate file

As the title say, does anyone knows how to generate a seprate declaration for the init/entry/step function into a seprate user-defined header file?

Normally they are located in MODEL_NAME.h. 
/* Model entry point functions */
extern void MODEL_initialize(void);
extern void MODEL_terminate(void);

/* Customized model step function */
extern void MODEL_update(void);

Thanks