How to save a browsed image into a variable to be called in another function

Question

This is my GUI code which has 3 buttons : 1.Browse an Image, 2.Load and Display the chosen Image 3.Run the Image through my prediction model and print a prediction statement

    import io
    import os
    import PySimpleGUI as sg
    import cv2
    import tensorflow as tf
    from tensorflow import keras
    from PIL import Image
    from keras.preprocessing.image 
    import load_img

    CATEGORIES = ["1st degree burn","2nd degree burn"]
    file_types = [("JPEG (*.jpg)", "*.jpg"),
    ("All files (*.*)", "*.*")]
    sg.theme('TealMono')
    def prepare(filepath):
    IMG_SIZE = 50
    img_array = cv2.imread(filepath)
    new_array = cv2.resize(img_array, (IMG_SIZE, IMG_SIZE))
    return new_array.reshape(-1, IMG_SIZE, IMG_SIZE, 1)

    def main():
    layout = [
    [sg.Image(key="-IMAGE-")],
    [
    sg.Text(("Burn Me Not"),size=(20,5),font=(50,20)),
    sg.Text("Image File"),
    sg.Input(size=(55, 1), key="-FILE-"),
    sg.FileBrowse(size=(25,3), file_types=file_types),
    sg.Button(("Load Image"),size=(25,3)),
    sg.Button(("run model"),size=(25,3)),
    sg.Button(("Exit"),size=(25,3)),
    sg.Listbox(values=("",""), size=(30,5))
    ],
    ]

    window = sg.Window('Test', layout).Finalize()
    window.Maximize()
    while True:
    event, values = window.read()
    if event == "Exit" or event == sg.WIN_CLOSED:
    break
    if event == "Load Image":
    filename = values["-FILE-"]
    if os.path.exists(filename):
    image = Image.open(values["-FILE-"])
    image.thumbnail((400,400))
    bio = io.BytesIO()
    image.save(bio, format="PNG")
    window["-IMAGE-"].update(data=bio.getvalue())
    if event == "run model":
    model = tf.keras.models.load_model("2variable.model")
    #img = load_image("image")
    prediction = model.predict([prepare("two_degree_test.jpg")])
    print(CATEGORIES[int(prediction[0][0])])

    window.close()
    if __name__ == "__main__":
    main()

However, the button does nothing as if the image that I previously loaded does not save over functions/buttons