AttributeError: 'NoneType' object has no attribute 'create_image'

I am creating a GUI with Python's tkinter. I have encountered an issue while trying to place an image read by OpenCV onto a tkinter canvas.

The error is as follows:

AttributeError: 'NoneType' object has no attribute 'create_image'

I am working with two files, features_ex.py and main.py, using classes, and it seems the issue lies with the class. This is because everything works fine when working within a single file.

features_ex.py:

  from tkinter import *
  from tkinter import Canvas
  from tkinter import Button
  from tkinter import ALL
  from tkinter import filedialog
  import os
  import sys
  import cv2 as cv
  import tkinter as tk
  from PIL import ImageTk
  from PIL import Image    

  class features():

      def __init__(self, root) :
          self.path = ''
          self.root = root 
          self.canvas = ''


      def LoadImage(self): 
          self.path = filedialog.askopenfilename()
          print(self.path)
          self.origin=cv.imread(str(self.path), cv.COLOR_BGR2RGB)
          self.origin = cv.resize(self.origin, (500, 500))
          features.show_image(self)
        

      def Canvas(self):
          self.canvas = Canvas(self.root, width=500, height=500, bg='gray91', border=1.25, relief='solid')
          self.canvas.pack(anchor='nw')

      def btn(self):
          self.btn = Button(self.root, text='Load', font='SimSun 15', border=1.25, command=lambda:features.LoadImage(self))
          self.btn.place(relx=0.015, rely=0.75)

      def show_image(self):
          print(str(self.path))
          self.img = Image.fromarray(self.origin)
          self.img = ImageTk.PhotoImage(image=self.img)
          self.canvas.create_image(0, 0, image=self.img, anchor='nw' )
    

main_ex.py:

from tkinter import *
from Features_ex import * 


class app:   
    def __init__ (self, interactive = False):

        ### Title Bar
        self.root=Tk() 
        self.root.title("Example")
        self.root.geometry('1280x720')
        self.root.resizable(1,1)

        ### Create button
        self.btn_load = features.btn(self)
        self.canvas = features.Canvas(self)

        self.root.mainloop()

if __name__ == '__main__' :
    app()

`

I researched the error and most sources point out issues with Canvas.pack(), suggesting to modify it as below.

self.canvas = Canvas()
self.canvas.pack()

However, I already meet this condition. So, I am unsure what the cause is. The error occurs with images in .jpg, .png, and .jpeg formats.

My versions are:

Python 3.11.8
Windows 11
Visual Studio Code