Specifies one or more of the following keywords. Each keyword
    indicates a type of difference to be ignored during the
    comparison.

    Keyword          Ignored Difference

    FIRST_VARIANT    Directs CMS to ignore any differences where the
                     generation in one class is the first variant of
                     the generation in the other class. For example
                     generation 2C1 is a first variant of generation
                     2 and generation 4B6D1 is a first variant of
                     generation 4B6.