code: public Excerpt typeParameters() {
      if (getTypeParameters().isEmpty()) {
        return Excerpts.EMPTY;
      } else {
        return Excerpts.add("<%s>", Excerpts.join(", ", getTypeParameters()));
      }
    }
docs: Returns a source excerpt of the type parameters of this type, including angle brackets.
  Always an empty string if the type class is not generic.
  
  <p>e.g. {@code <N, C>}