Function interp_btreemap 

fn interp_btreemap(
    _args: &[RValue],
    _named: &[(String, RValue)],
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Create an empty BTreeMap (ordered key-value store).

Keys are always maintained in sorted order. Returns an integer ID with class “btreemap”.

@return integer scalar with class “btreemap”