def METHOD_NAME(shortcut):
    """Convert a Toga shortcut definition into GTK accelerator definition."""
    accel = shortcut
    # Convert the shortcut into string form.
    try:
        accel = shortcut.value
    except AttributeError:
        accel = shortcut
    modifiers = []
    # Remove any modifiers from the shortcut definition
    for key, code in GTK_MODIFIER_CODES.items():
        if key.value in accel:
            accel = accel.replace(key.value, "")
            modifiers.append(code)
    # Find the canonical definition of the remaining key.
    for key, code in GTK_KEY_CODES.items():
        if key.value == accel:
            accel = accel.replace(key.value, code)
    accel = "".join(modifiers) + accel
    return accel