use crate::MAX_DATA_LEN; /// The error returned by most functions in the [`encode`][crate::encode] module#[derive(Debug, thiserror::Error)]#[allow(missing_docs)]pub enum Error {    #[error("Cannot encode more than {MAX_DATA_LEN} bytes, got {length_in_bytes}")]    DataLengthLimitExceeded { length_in_bytes: usize },    #[error("Empty lines are invalid")]    DataIsEmpty,} #[cfg(all(not(feature = "blocking-io"), feature = "async-io"))]mod async_io;#[cfg(all(not(feature = "blocking-io"), feature = "async-io"))]pub use async_io::*; #[cfg(feature = "blocking-io")]mod blocking_io;#[cfg(feature = "blocking-io")]pub use blocking_io::*; pub(crate) fn u16_to_hex(value: u16) -> [u8; 4] {    let mut buf = [0u8; 4];    hex::encode_to_slice((value as u16).to_be_bytes(), &mut buf).expect("two bytes to 4 hex chars never fails");    buf}