Macro node

macro_rules! node {
    ($graph:ident, $var:ident, $name:expr) => { ... };
    ($graph:ident, $var:ident, $name:expr, $block:block) => { ... };
    ($graph:ident, $var:ident, $name:expr, $parent:expr) => { ... };
    ($graph:ident, $var:ident, $name:expr, $parent:expr, $block:block) => { ... };
}