>>> df = session.create_dataframe([[10, 11], [20, 22], [25, None], [30, 35]], schema=["v", "v2"])
>>> df.groupBy("v").agg(regr_avgx(df["v"], df["v2"]).alias("regr_avgx")).sort("v").collect()
[Row(V=10, REGR_AVGX=11.0), Row(V=20, REGR_AVGX=22.0), Row(V=25, REGR_AVGX=None), Row(V=30, REGR_AVGX=35.0)]