use serde::Serialize; #[derive(Debug, thiserror::Error)]pub enum AppError {    #[error("IO error: {0}")]    Io(String),    #[error("Not found: {0}")]    NotFound(String),    #[error("Already exists: {0}")]    AlreadyExists(String),    #[error("No workspace is open")]    NoWorkspace,} impl Serialize for AppError {    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>    where        S: serde::Serializer,    {        serializer.serialize_str(&self.to_string())    }} impl From<std::io::Error> for AppError {    fn from(err: std::io::Error) -> Self {        AppError::Io(err.to_string())    }}