Parameters in clip() parse strings as column names, which is undocumented

[etiennebacher]

Description

In clip(), both parameters have the description:

Accepts expression input. Non-expression inputs are parsed as literals.

It should be mentioned that string inputs are parsed as column names:

import polars as pl
df = pl.DataFrame({"a": [-50, 5, 50, None], "bound": [2, 10, 1, 1]})
df.with_columns(clip=pl.col("a").clip("bound"))

shape: (4, 3)
┌──────┬───────┬──────┐
│ a    ┆ bound ┆ clip │
│ ---  ┆ ---   ┆ ---  │
│ i64  ┆ i64   ┆ i64  │
╞══════╪═══════╪══════╡
│ -50  ┆ 2     ┆ 2    │
│ 5    ┆ 10    ┆ 10   │
│ 50   ┆ 1     ┆ 50   │
│ null ┆ 1     ┆ null │
└──────┴───────┴──────┘

Link

https://docs.pola.rs/api/python/dev/reference/expressions/api/polars.Expr.clip.html