Juriy right. for reingenering package code not needed
use object PACKAGE BODY (only PACKAGE).

SQL> set pages 9999
SQL> set lines 120
SQL> set long 20000
SQL> create or replace package abc is
2 function f(a number) return number;
3 end;
4 /

Package created.

SQL> create or replace package body abc is
2 function f(a number) return number is
3 begin
4 return 1;
5 end;
6 end;
7 /

Package body created.

SQL> select dbms_metadata.get_ddl('PACKAGE', 'ABC', 'TRAIN') dual;

DBMS_METADATA.GET_DDL('PACKAGE','ABC','TRAIN')
---------------------------------------------------------------------------

CREATE OR REPLACE PACKAGE "TRAIN"."ABC" is
function f(a number) return number;
end;
CREATE OR REPLACE PACKAGE BODY "TRAIN"."ABC" is
function f(a number) return number is
begin
return 1;
end;
end;