import stringprep


def b1_mapping(char):
    """Do RFC 3454 B.1 table mapping.

    :Parameters:
        - `char`: Unicode character to map.

    :returns: u"" if there is `char` code in the table, `None` otherwise.
    """
    if stringprep.in_table_b1(char):
        return u""
    else:
        return None