message: Hide Arguments fields from users
  Summary: To make changes in it easier: separate interface from implementation.
diff: @@ -712,17 +712,17 @@ impl<'v, 'a> ParametersParser<'v, 'a> {
  #[derive(Default, Clone, Copy, Dupe)]
  pub struct Arguments<'v, 'a> {
  /// Positional arguments.
  - pub pos: &'a [Value<'v>],
  + pub(crate) pos: &'a [Value<'v>],
  /// Named arguments.
  - pub named: &'a [Value<'v>],
  + pub(crate) named: &'a [Value<'v>],
  /// Names of named arguments.
  ///
  /// `named` length must be equal to `names` length.
  - pub names: &'a [(Symbol, StringValue<'v>)],
  + pub(crate) names: &'a [(Symbol, StringValue<'v>)],
  /// `*args` argument.
  - pub args: Option<Value<'v>>,
  + pub(crate) args: Option<Value<'v>>,
  /// `**kwargs` argument.
  - pub kwargs: Option<Value<'v>>,
  + pub(crate) kwargs: Option<Value<'v>>,
  }
  impl<'v, 'a> Arguments<'v, 'a> {
  