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Reproducible example

import polars as pl
from datetime import datetime
date = pl.datetime_range(
    datetime(2001, 1, 1),
    datetime(2001, 1, 2),
   "1h",
   eager=True
)

 # This works fine
pl.select(pl.lit(pl.Series("index", range(25))).rolling_mean_by(s, "2h"))

# This doesn't exist
pl.Series("index", range(25)).rolling_mean_by(s, "2h")

Log output

AttributeError: 'Series' object has no attribute 'rolling_mean_by'

Issue description

The rule is usually that functions are both implemented on Expr and Series. That was not done here.

Expected behavior

Series has these methods as well.

Installed versions

Replace this line with the output of pl.show_versions(). Leave the backticks in place.