Pipeline function debugging error:

ORA - 06550. Line 16, 12 columns;
PLS - 00653; In PL/SQL domain is not allowed to have gathered/table function
Code:
The function test_zx return tb_test_z
Pipelined

As
V_tb_test obj_test_z;
The begin
For I in 1.. 5 loop
V_tb_test:=obj_test_z (SDF,
'SDF'
500,
'SDF'
'SDF'
Sysdate,
1,
'SDF);
Pipe row (v_tb_test);

End loop;
return;
End test_zx;