[Python] Python polars -- how to apply function across multiple cols

How to extend this

df = df.select(
pl.col("x1").map_batches(custom_function).alias("new_x1")
)


to something like

df = df.select(
pl.col("x1","x2").map_batches(custom_function).alias("new_x1", "new_x2")
)


Or the way to go is doing it one by one

df = df.select(
pl.col("x1").map_batches(custom_function).alias("new_x1")
pl.col("x2").map_batches(custom_function).alias("new_x2")
)

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