Function get_format 

pub fn get_format(name: &str) -> Result<Format, OmnistError>

The registered Format for name. An OmnistError::Format if unknown, naming every currently-registered format name, sorted – mirrors Python’s get_format’s f"unknown format {name!r}; registered: {known}" message. Unlike Python, there is no "(none)" fallback for an empty registry: register_format only ever adds entries and the five builtins always register on first access (see builtins), so the registry can never actually be empty here – an untestable dead branch for that case was deliberately not carried over (playbook’s “unreachable dead code” gap classification), rather than kept under an unreachable coverage-ignore.