def set_icon_image(icon):
    """ Set Icon image or set None """
    # Icon message files: https://stackoverflow.com/questions/37783878/
    # is-it-possible-to-get-tkinter-messagebox-icon-image-files
    # ::tk::icons::warning
    # ::tk::icons::error
    # ::tk::icons::information
    # ::tk::icons::question
    if icon is "warning":
        icon_image = "::tk::icons::warning"
    elif icon is "error":
        icon_image = "::tk::icons::error"
    elif icon is "information":
        icon_image = "::tk::icons::information"
    elif icon is "question":
        icon_image = "::tk::icons::question"
    else:
        icon_image = None
    return icon_image