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    use proc_macro2::TokenStream;
    use quote::ToTokens;

    pub struct TokensOrDefault<'a, T: 'a>(pub &'a Option<T>);

    impl<'a, T> ToTokens for TokensOrDefault<'a, T>
    where
        T: ToTokens + Default,
    {
        fn to_tokens(&self, tokens: &mut TokenStream) {
            match *self.0 {
                Some(ref t) => t.to_tokens(tokens),
                None => T::default().to_tokens(tokens),
            }
        }
    }

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