>>> df = session.create_dataframe([[10, 11], [20, 22], [25, None], [30, 35]], schema=["v", "v2"])
>>> df = df.filter(df["v2"].is_not_null())
>>> df.group_by("v").agg(regr_sxy(df["v"], df["v2"]).alias("regr_sxy")).collect()
[Row(V=10, REGR_SXY=0.0), Row(V=20, REGR_SXY=0.0), Row(V=30, REGR_SXY=0.0)]