Get the center lat/lon of model

def centerLatLon(self):
        """
        Get the center lat/lon of model
        """
        # GET CENTROID FROM GSSHA GRID
        gssha_grid = self.getGrid()

        min_x, max_x, min_y, max_y = gssha_grid.bounds()
        x_ext, y_ext = transform(gssha_grid.proj,
                                 Proj(init='epsg:4326'),
                                 [min_x, max_x, min_x, max_x],
                                 [min_y, max_y, max_y, min_y],
                                 )
        return np.mean(y_ext), np.mean(x_ext)