Macro impl_conversion_traits 

macro_rules! impl_conversion_traits {
    ($( $trait_:ident ),* for $($type_spec:tt)+) => { ... };
    (@expand_traits [$trait_:ident $($rest_traits:ident)*] $($type_spec:tt)+) => { ... };
    (@expand_traits [] $($type_spec:tt)+) => { ... };
    (@impl AsAudioGeneration for $($type_spec:tt)+) => { ... };
    (@impl AsImageGeneration for $($type_spec:tt)+) => { ... };
    (@impl $trait_:ident for $($type_spec:tt)+) => { ... };
    (@impl_trait $trait_:ident for $struct_:ident) => { ... };
    (@impl_trait $trait_:ident for $struct_:ident<$($generics:tt),*>) => { ... };
}