protected @Nullable ContentEntry doAddContentEntry(ModifiableRootModel modifiableRootModel) {
    final String contentEntryPath = getContentEntryPath();
    if (contentEntryPath == null) return null;
    new File(contentEntryPath).mkdirs();
    final VirtualFile moduleContentRoot = LocalFileSystem.getInstance().refreshAndFindFileByPath(contentEntryPath.replace('\\', '/'));
    if (moduleContentRoot == null) return null;
    return modifiableRootModel.addContentEntry(moduleContentRoot);
  }
protected @Nullable ContentEntry doAddContentEntry(ModifiableRootModel modifiableRootModel)