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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 get_tile_url(self, zoom, x, y):
 """ Fill the placeholders of the tile url with zoom, x and y. 'http://tile.openstreetmap.org/42/43/44.png' """

        return self.tile_url.format(**{"$z": zoom, "$x": x, "$y": y})