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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 quadkey_to_tile(quadkey):
 """Transform quadkey to tile coordinates"""

        tile_x, tile_y = (0, 0)
        level = len(quadkey)
        for i in xrange(level):
            bit = level - i
            mask = 1 << (bit - 1)
            if quadkey[level - bit] == '1':
                tile_x |= mask
            if quadkey[level - bit] == '2':
                tile_y |= mask
            if quadkey[level - bit] == '3':
                tile_x |= mask
                tile_y |= mask
        return [(tile_x, tile_y), level]