Macro id

macro_rules! id {
    () => { ... };
    (html$e:expr) => { ... };
    (esc$e:expr) => { ... };
    ($e:expr) => { ... };
}

represents an id for node or subgraph in dot lang. #Arguments:

• html - html format.
• esc - escaped string. It allows the escaped quotes inside and also wraps the string to the quotas #Example:

    fn id_test() {
        use dot_generator::*;
        use dot_structures::*;

        assert_eq!(id!(), Id::Anonymous("".to_string()));
        assert_eq!(id!(html "<<abc>>"), Id::Html("<<abc>>".to_string()));
        assert_eq!(id!("abc"), Id::Plain("abc".to_string()));
        assert_eq!(id!(esc r#"ab\"c"#"), Id::Escaped(r#"\"ab\"c\""#.to_string()));
    }