/**
  * Gets the index of the given string, which must have been added to this instance.
  *
  * @param string {@code non-null;} the string to look up
  * @return {@code >= 0;} the string's index
  */
 public int indexOf(CstString string) {
   return indexOf(string.getString());
 }
 /**
  * Interns an element into this instance.
  *
  * @param string {@code non-null;} the string to intern, as a {@link CstString}
  * @return {@code non-null;} the interned string
  */
 public StringIdItem intern(CstString string) {
   CstUtf8 utf8 = string.getString();
   return intern(new StringIdItem(utf8));
 }