code: @SuppressWarnings("unchecked")
    public Query include(int level) {
      if (level < 0) {
        throw new IllegalArgumentException(format("Include level of %d is negative.", level));
      }
      if (level > 10) {
        throw new IllegalArgumentException(format("Include level of %d is to high.", level));
      }
  
      params.put(PARAMETER_INCLUDE, Integer.toString(level));
  
      return (Query) this;
    }
docs: Include references entries and their entries up to the given level.
  <p>
  A level of inclusion of 0 means, do not include references referenced, but not requested.
  Please note also, that more then 10 include levels cannot be specified.
  
  @param level the number of recursion of inclusion to be used.
  @return the calling query for chaining.