Clone Graph

1def cloneGraph(node: 'Node') -> 'Node':
2    if not node:
3        return None
4        
5    copies = {}
6    
7    def dfs(cur: 'Node') -> 'Node':
8        if cur in copies:
9            return copies[cur]
10        copy = Node(cur.val)
11        copies[cur] = copy
12        for nei in cur.neighbors:
13            copy.neighbors.append(dfs(nei))
14        return copy
15    
16    return dfs(node)