public static @Nullable String findRelativePath(PsiFileSystemItem src, PsiFileSystemItem dst) {
    VirtualFile srcFile = src != null ? src.getVirtualFile() : null;
    VirtualFile dstFile = dst != null ? dst.getVirtualFile() : null;
    return srcFile != null && dstFile != null ? VfsUtilCore.findRelativePath(srcFile, dstFile, VFS_SEPARATOR_CHAR) : null;
  }
public static @Nullable String findRelativePath(PsiFileSystemItem src, PsiFileSystemItem dst)