#define be_ifg_free(self) ((self)->impl->free(self))
#define be_ifg_connected(self,a,b) ((self)->impl->connected(self, a, b))
#define be_ifg_neighbours_begin(self, iter, irn) ((self)->impl->neighbours_begin(self, iter, irn))
#define be_ifg_free(self) ((self)->impl->free(self))
#define be_ifg_connected(self,a,b) ((self)->impl->connected(self, a, b))
#define be_ifg_neighbours_begin(self, iter, irn) ((self)->impl->neighbours_begin(self, iter, irn))