code: public void generate(Output out) throws IOException {
          out.output(getSelectorString());
          out.output(" {");
          out.incIndent();
          for (Attribute attr : attributes) {
              out.optionalLineBreak();
              out.output(attr);
          }
          for (Section child : subSections) {
              out.lineBreak();
              child.generate(out);
          }
          out.decIndent();
          out.optionalLineBreak();
          out.output("}");
      }
docs: Generates the final output into the given parameter.
  
  @param out the target for the generated output
  @throws IOException in case of an io error in the underlying writer