code: public IncludePath createIncludePath() {
      final Project p = getProject();
      if (p == null) {
        throw new java.lang.IllegalStateException("project must be set");
      }
      if (isReference()) {
        throw noChildrenAllowed();
      }
      final IncludePath path = new IncludePath(p);
      this.includePaths.addElement(path);
      return path;
    }
docs: Creates an include path.