how to get list of arguments in a procedure with DEFAULT VALUE

I want to get list of arguments in a procedure with DEFAULT VALUE .

For instance:

DBMS_METADATA.GET_DDL (
object_type     IN VARCHAR2,
name            IN VARCHAR2,
schema          IN VARCHAR2 DEFAULT NULL,
version         IN VARCHAR2 DEFAULT 'COMPATIBLE',
model           IN VARCHAR2 DEFAULT 'ORACLE',
transform       IN VARCHAR2 DEFAULT 'DDL')
RETURN CLOB;

1.we have dba_source but TEXT shows a huge list.........not specific to just GET_DDL

2.i checked dba_arguments but doesnt show the default value:

SQL> select OWNER,OBJECT_NAME,PACKAGE_NAME,ARGUMENT_NAME,DATA_TYPE,DEFAULTED,DEFAULT_VALUE,IN_OUT from dba_arguments where OBJECT_NAME='GET_DDL' and PACKAGE_NAME='DBMS_METADATA';OWNER OBJECT_NAME PACKAGE_NAME ARGUMENT_NAME DATA_TYPE D DEFAULT_VA IN_OUT----- ------------------------------ ------------------------------ ------------------------------ ------------------------------ - ---------- ---------SYS GET_DDL DBMS_METADATA TRANSFORM VARCHAR2 Y INSYS GET_DDL DBMS_METADATA MODEL VARCHAR2 Y INSYS GET_DDL DBMS_METADATA VERSION VARCHAR2 Y INSYS GET_DDL DBMS_METADATA SCHEMA VARCHAR2 Y INSYS GET_DDL DBMS_METADATA NAME VARCHAR2 N INSYS GET_DDL DBMS_METADATA OBJECT_TYPE VARCHAR2 N INSYS GET_DDL DBMS_METADATA CLOB N OUT7 rows selected.