What is the XML rule for remove CN attribute from modify events?

<rule>    <description>remove CN attribute from modify events</description>    <conditions>        <and>            <if-operation mode="nocase" op="equal">modify</if-operation>            <if-op-attr name="CN" op="available"/>          </and>      </conditions>    <actions>        <do-strip-op-attr name="CN"/>      </actions>  </rule>