code: public static String getParent(String filePath, int level) {
  		final File parent = getParent(file(filePath), level);
  		try {
  			return null == parent ? null : parent.getCanonicalPath();
  		} catch (IOException e) {
  			throw new IORuntimeException(e);
  		}
  	}
docs: 获取指定层级的父路径
  
  <pre>
  getParent("d:/aaa/bbb/cc/ddd", 0) -> "d:/aaa/bbb/cc/ddd"
  getParent("d:/aaa/bbb/cc/ddd", 2) -> "d:/aaa/bbb"
  getParent("d:/aaa/bbb/cc/ddd", 4) -> "d:/"
  getParent("d:/aaa/bbb/cc/ddd", 5) -> null
  </pre>
  
  @param filePath 目录或文件路径
  @param level 层级
  @return 路径File，如果不存在返回null
  @since 4.1.2