Oracle LEAF TYPE

CREATE OR REPLACE TYPE leaf_type UNDER mid_type
(
 leaf_attr VARCHAR2(1000),
 CONSTRUCTOR FUNCTION leaf_type
 (
 i_base_id INTEGER,
 i_base_attr VARCHAR2,
 i_mid_attr DATE,
 i_leaf_attr VARCHAR2
 ) RETURN SELF AS RESULT,
 MEMBER FUNCTION get_leaf_attr RETURN VARCHAR2,
 MEMBER PROCEDURE set_leaf_attr(i_leaf_attr VARCHAR2),
 OVERRIDING MEMBER FUNCTION to_string RETURN VARCHAR2
) INSTANTIABLE FINAL

CREATE OR REPLACE TYPE BODY leaf_type AS
 CONSTRUCTOR FUNCTION leaf_type
 (
 i_base_id INTEGER,
 i_base_attr VARCHAR2,
 i_mid_attr DATE,
 i_leaf_attr VARCHAR2
 ) RETURN SELF AS RESULT
 IS
 BEGIN
 self.base_id := i_base_id;
 self.base_attr := i_base_attr;
 self.mid_attr := i_mid_attr;
 self.leaf_attr := i_leaf_attr;
 RETURN;
 END leaf_type;
 MEMBER FUNCTION get_leaf_attr RETURN VARCHAR2 IS
 BEGIN
 RETURN self.leaf_attr;
 END get_leaf_attr;
 MEMBER PROCEDURE set_leaf_attr(i_leaf_attr VARCHAR2) IS
 BEGIN
 self.leaf_attr := i_leaf_attr;
 END set_leaf_attr;
 OVERRIDING MEMBER FUNCTION to_string RETURN VARCHAR2 IS
 BEGIN
 RETURN (SELF AS mid_type).to_string || '; LEAF_ATTR [' || self.leaf_attr || ']';
 END to_string;
END;