Macro delegate_impl_metadata_trait 

macro_rules! delegate_impl_metadata_trait {
    (expr, $self:ident => $impl:tt, &mut => $mut_impl:tt) => { ... };
    ($src:tt, extended) => { ... };
    ($src:tt) => { ... };
}

Delegates the implementation of MSDataFileMetadata to a member. Passing an extra level extended token implements the optional methods.