Some example use cases: <contains> <op field="title">MASTER</op> </contains>
<contains> <op field="importance">r'(High|Wishlist)'</op> </contains>
Some example use cases: title"> MASTER< /op>
<contains>
<op field="
</contains>
<contains> importance" >r'(High| Wishlist) '</op>
<op field="
</contains>