def is_mbi_format_synthetic(mbi):
    """
    Returns True if mbi format is synthetic.

    This is the case where there is an "S" in the 2nd position
    denoting a synthetic MBI value.
    """
    # Check if NoneType.
    if mbi is None:
        return None
    else:
        return len(mbi) == 11 and mbi[1] == "S"