docs: protected IntDependency intern(IntTaggedWord headTW, IntTaggedWord argTW, boolean leftHeaded, short dist) {
      Map<IntDependency,IntDependency> map = expandDependencyMap;
      IntDependency internTempDependency = new IntDependency(itwInterner.intern(headTW), itwInterner.intern(argTW), leftHeaded, dist);
      IntDependency returnDependency = internTempDependency;
      if (map != null) {
        returnDependency = map.get(internTempDependency);
        if (returnDependency == null) {
          map.put(internTempDependency, internTempDependency);
          returnDependency = internTempDependency;
        }
      }
      return returnDependency;
    }