Prompts the user to provide the raster bounds with a dialog. 
        Saves the bounds to be applied to the plot

def askRasterBounds(self):
        """Prompts the user to provide the raster bounds with a dialog. 
        Saves the bounds to be applied to the plot"""
        dlg = RasterBoundsDialog(bounds= (self.rasterBottom, self.rasterTop))
        if dlg.exec_():
            bounds = dlg.values()
            self.setRasterBounds(bounds)