Constant IMAGE_SERIALIZATION_FORMAT 

pub const IMAGE_SERIALIZATION_FORMAT: &str;

RFC-0088 — the serialization format the backend this image links speaks, as its cross-image identity string.

This is a compile-time constant precisely because the backend is selected at compile time (see the aliases above): where ROS 2 asks rmw_get_serialization_format() at run time — because it resolves its typesupport through dlopen — nano-ros already knows.

Only meaningful in a single-backend image. A bridge image links two backends and has no single answer; it must ask each session instead.