Macro attribute 

macro_rules! attribute {
    ($value:ident) => { ... };
    ($key:ident = $value:literal) => { ... };
    ($key:ident = $value:expr) => { ... };
    ($key:ident-$key_tail:ident = $value:literal) => { ... };
    ($key:ident-$key_tail:ident = $value:expr) => { ... };
}

Create Attribute