Function hasKey

hasKey(graph, key): boolean
Returns true if graph contains key.
```
// Same as
g.vertices.has(key)
```
Parameters
- graph: Readonly<{
      vertices: IMapImmutable<string, Readonly<{
          id: string;
          out: readonly Readonly<{
              id: string;
              weight?: number;
          }>[];
      }>>;
  }>
- key: string
Returns boolean