code: public Elements getElementsByAttributeValueMatching(String key, Pattern pattern) {
          return Collector.collect(new Evaluator.AttributeWithValueMatching(key, pattern), this);
          
      }
docs: Find elements that have attributes whose values match the supplied regular expression.
  @param key name of the attribute
  @param pattern compiled regular expression to match against attribute values
  @return elements that have attributes matching this regular expression