<condition> = [<sub_cond> [<spanclass="hljs-keyword">and</span>/<spanclass="hljs-keyword">or</span><sub_cond>]] <spanclass="hljs-comment"># `and` is same as chaining conditions.</span>
<condition> = [<sub_cond> [<spanclass="hljs-keyword">and</span>/<spanclass="hljs-keyword">or</span><sub_cond>]] <spanclass="hljs-comment"># For negation use `not(<sub_cond>)`.</span>
<sub_cond> = contains(@<attr>, <spanclass="hljs-string">"<val>"</span>) <spanclass="hljs-comment"># Is <val> a substring of attr's value?</span>
<sub_cond> = [//]<element><spanclass="hljs-comment"># Has matching child? Descendant if //.</span>