Function cum_reduce_exprs 

pub fn cum_reduce_exprs<E>(
    f: PlanCallback<(Series, Series), Series>,
    exprs: E,
    returns_scalar: bool,
    return_dtype: Option<DataTypeExpr>,
) -> Expr
where
    E: AsRef<[Expr]>,

Available on crate feature lazy only.

Accumulate over multiple columns horizontally / row wise.