code: public FilterSpec normalize() {
          List<FilterSpec> clonedExpressions = expressions != null ? cloneExpressions(expressions, true) : null;
  
          FilterSpec copy = new FilterSpec(path, operator, value, clonedExpressions);
          return copy;
      }
docs: Normalizes this FilterSpec by normalizing all FilterSpec objects within
  <code>expressions</code> and then sorting the list itself.
  
  @return normalized FilterSpec