code: func (g *UndirectedGraph) From(n graph.Node) []graph.Node {
  	if !g.Has(n) {
  		return nil
  	}
  
  	nodes := make([]graph.Node, g.edges[n.ID()].Len())
  	i := 0
  	g.edges[n.ID()].Visit(func(neighbor int, edge graph.Edge) {
  		nodes[i] = g.nodes[neighbor]
  		i++
  	})
  
  	return nodes
  }
docs: // From returns all nodes in g that can be reached directly from n.