@Override
    public boolean evaluate(WithTags input, List<String> matchKeys) {
      Object value = input.getTag(field);
      if (value != null && !"".equals(value) && !(value instanceof Collection<?> c && c.isEmpty())) {
        matchKeys.add(field);
        return true;
      }
      return false;
    }
Evaluates to true if an input element contains any value for {@code field} tag.
planetiler-core/src/main/java/com/onthegomap/planetiler/expression/Expression.java