def findMax(t):
    if t == None:
        return None # shouldn't reach this
    else:
        values = []
        values.append(t["contents"])
        
        if t["left"] != None:
            leftLargest = findMax(t["left"])
            values.append(leftLargest)
        if t["right"] != None:
            rightLargest = findMax(t["right"])
            values.append(rightLargest)
        return max(values)
    
t = { "contents" : 4,
    "left"  : { "contents" : 7,
                    "left"  : None,
                    "right" : { "contents" : 2,
                                     "left"  : None,
                                     "right" : None } },
    "right" : { "contents" : 3,
                     "left"  : None,
                     "right" : { "contents" : 10,
                                      "left"  : None,
                                      "right" : None } } }