Macro props 

macro_rules! props {
    ($($key:expr => $val:expr),* $(,)?) => { ... };
}

Convenience macro for building property maps.

use hora_graph_core::{props, PropertyValue};
let p = props! { "language" => "Rust", "stars" => 42 };
assert_eq!(p.get("language"), Some(&PropertyValue::String("Rust".into())));