75     fn open(&self, _data: &mut FilePrivateData) -> Result<(), i32> {  in open()  argument
76         Err(-(ENOTSUP as i32))  in open()
79     fn close(&self, _data: &mut FilePrivateData) -> Result<(), i32> {  in close()  argument
80         Err(-(ENOTSUP as i32))  in close()
83     fn metadata(&self) -> Result<Metadata, i32> {  in metadata()  argument
91     fn list(&self) -> Result<Vec<String>, i32> {  in list()  argument
92         Err(-(ENOTSUP as i32))  in list()
95     fn set_metadata(&self, metadata: &Metadata) -> Result<(), i32> {  in set_metadata()  argument
107     fn poll(&self) -> Result<PollStatus, i32> {  in poll()  argument
120     ) -> Result<usize, i32> {  in read_at()  argument
122             return Err(-(EINVAL as i32));  in read_at()
139     ) -> Result<usize, i32> {  in write_at()  argument
141             return Err(-(EINVAL as i32));  in write_at()