Function value_to_simple_toml 

pub fn value_to_simple_toml(v: &Value, prefix: &str) -> String

Active brace-style emission (key = value lines plus [table] headers): doubles as the unit round-trip path (every suffix from Unit::suffix() re-parses — see tests/unit_roundtrip.rs), so it stays exactly as is. Real TOML interchange lives in export::value_to_toml_string.