I found the solution. I want to share with you.

@UncheckedAccess
FUNCTION Part_No_To_Technical_Class (
   target_key_ref_   IN VARCHAR2,
   service_name_     IN VARCHAR2 ) RETURN VARCHAR2
IS
   source_key_ref_ VARCHAR2(100);
BEGIN
   $IF (Component_Appsrv_SYS.INSTALLED) $THEN
      source_key_ref_:= 'TECHNICAL_CLASS=' || Technical_Object_Reference_API.Get_Technical_Class_With_Key('PartCatalog', 
         'PART_NO=' || Client_SYS.Get_Key_Reference_Value(target_key_ref_,'PART_NO') || '^') || '^';
   $END
   --error_sys.record_general('', source_key_ref_);
   RETURN source_key_ref_;
END Part_No_To_Technical_Class;

Good luck!