Macro immutable_attributes 

macro_rules! immutable_attributes {
    ($requested:expr,
     Immutable {$($immut_a:ident: $immut_v:expr),* $(,)?}) => { ... };
}

Helper for building [fio::NodeAttributes2]given immutable attributes inrequestedCode will only run forrequestedattributes. Mutable attributes inrequested` are ignored.

Example:

immutable_attributes!( requested, Immutable { content_size: 789 } );