def multi1(vals):
    """
    This will either return the common value from a list of identical values
    or the single character '?'
    """
    uniq_vals = list(set(vals))
    num_vals = len(uniq_vals)
    if num_vals == 0:
        return None
    if num_vals == 1:
        return uniq_vals[0]
    if num_vals > 1:
        return "?"