Serial port access from GUI tkinter python

Hi, I can access my serial ports and do what ever I want from phyton, but when I try to implement the access in my Tkinter-Python GUI code, it gives me error

Can you please post the code that is causing the error, as well as the error message you are getting?

I’m developing a main menu (GUI with TKinter) calling different modules which each selection
the main work in those module will be accessing serial ports (15 in total), configuring, transmitting and receiving bytes to control other devices.
When I tried to start working with ports in the first module I called, I did it doing this

import serial
``
and this is what I received...

Traceback (most recent call last):
File “C:\Code\ATE APAS\newATE.py”, line 6, in
import ATE_Diagnostic
File “C:\Code\ATE APAS\ATE_Diagnostic.py”, line 5, in
import serial
File “C:\Code\ATE APAS\serial.py”, line 8, in
import serial.tools.list_ports
ModuleNotFoundError: No module named ‘serial.tools’; ‘serial’ is not a package

(program exited with code: 1)

Press any key to continue . . .

tried to open serial port in the first code (main window) and reeived the same error.
From Python interpreter everything work perfectly
opening serial ports 
configuring them
send and receive bytes, etc