message: Remove out of date comment
  Summary: This no longer applies.
diff: @@ -30,7 +30,6 @@ pub trait UnpackValue<'v>: Sized {
  fn expected() -> String;
  /// Given a [`Value`], try and unpack it into the given type, which may involve some element of conversion.
  - /// The `heap` argument is _usually_ not required.
  fn unpack_value(value: Value<'v>) -> Option<Self>;
  /// Unpack value, but instead of `None` return error about incorrect argument type.
  