nr nodes tree

arbore = { "value" : 8,
           "left":
            {
                "value": 9, "left":
                {
                    "value": 3, "left":
                    {
                        "value": 14, "left": None, "right": None
                    }, "right":
                    {
                        "value": 2, "left": None, "right":
                        {
                            "value": 5, "left": None, "right": None
                        }
                    }
                }, "right": None
            },
           "right":
            {
                "value": 20, "left":
                {
                    "value": 7, "left": None, "right": None
                }, "right":
                {
                    "value": 15, "left":
                    {
                        "value": 30, "left":
                        {
                            "value": 22, "left": None, "right": None
                        }, "right":
                        {
                            "value": 27, "left": None, "right": None
                        }
                    }, "right": None
                }
            }
           }

def nrNodes(tree):
    r = 0
    def utilNrNodes(tree):
        nonlocal r
        r += 1
        if tree['left'] is not None:
            utilNrNodes(tree['left'])
        if tree['right'] is not None:
            utilNrNodes(tree['right'])
    utilNrNodes(tree)
    return r

print(nrNodes(arbore))