def radio_button_message(n_clicks, value):
    """

    Function that returns a message when the user selects a radio button.

    Args:
        n_clicks: Number of clicks registered by the submit button.
        value: The radio button option selected by the user.

    Returns:
        A message to the user as a response to the radio button input.

    """

    if value is None:
        return 'Please select an option'
    else:
        return 'You have selected: ' + value