Function aggregate_standard 

fn aggregate_standard(
    x: &RValue,
    by: &RValue,
    fun: &RValue,
    extra_named: &[(String, RValue)],
    fail_fast: bool,
    env: &Environment,
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Standard (non-formula) aggregate: aggregate(x, by, FUN)