public StringIdItem intern(CstString string) {
    return intern(new StringIdItem(string));
  }
Interns an element into this instance.

@param string {@code non-null;} the string to intern, as a constant
@return {@code non-null;} the interned string
android/android_framework/dex-maker/src/main/java/com/android/dx/dex/file/StringIdsSection.java