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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def min_zoom(self):
 """ Get the minimal zoom level of all layers. Returns: int: the minimum of all zoom levels of all layers Raises: ValueError: if no layers exist """

        zoom_levels = [map_layer.min_zoom for map_layer in self.layers]
        return min(zoom_levels)