I am trying to build an image viewer using Tkinter but I am stuck at this weird problem

Keep a reference to the image

from tkinter import *from PIL import ImageTk, Imageimport osdef moveForward():    global current_img    global currImageIndex    global imgLabel    currImageIndex += 1    imgLabel.grid_forget()    print(picturesList)    img = ImageTk.PhotoImage(Image.open(picturesList[currImageIndex]))    current_img = img    imgLabel = Label(root,image=img)    imgLabel.grid(row=0,column=1)picturesList = []#Here is the variable where the reference will be storedcurrent_img = Nonefor pictures in os.listdir('images'):    if pictures.startswith('img'):        picturesList.append('images/'+pictures)currImageIndex = 0root = Tk()img = ImageTk.PhotoImage(Image.open("images/img5.jpg"))imgLabel = Label(image=img)imgLabel.grid(row=0,column=1)backwardImg = ImageTk.PhotoImage(Image.open("images/backward.ico"))backButton = Button(image=backwardImg,width=80,height=80,relief=FLAT)backButton.grid(row=0,column=0)forwardImg = ImageTk.PhotoImage(Image.open("images/forward.ico"))forwardButton = Button(image=forwardImg, width=80, height=80, relief=FLAT, command=moveForward)forwardButton.grid(row=0,column=2)root.mainloop()