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//! The internal implementation details of [`Layer`].
//!
//! [`Layer`] itself is quite simple:
//!
//! ```ignore
//! pub trait Layer<A: Access> {
//!     type LayeredAccess: Access;
//!
//!     fn layer(&self, inner: A) -> Self::LayeredAccess;
//! }
//! ```
//!
//! `XxxLayer` will wrap input [`Access`] as inner and return a new [`Access`]. So normally the implementation of [`Layer`] will be split into two parts:
//!
//! - `XxxLayer` will implement [`Layer`] and return `XxxAccessor` as `Self::LayeredAccess`.
//! - `XxxAccess` will implement [`Access`] and be built by `XxxLayer`.
//!
//! Most layer only implements part of [`Access`], so we provide
//! [`LayeredAccess`] which will forward all unimplemented methods to
//! `inner`. It's highly recommend to implement [`LayeredAccess`] trait
//! instead.
//!
//! [`Layer`]: crate::raw::Layer
//! [`Access`]: crate::raw::Access
//! [`LayeredAccess`]: crate::raw::LayeredAccess
