def exportValue(self, vf, value):
        m = StrStrHashMap(value)
        keysAndValues = []
        for i in m.keys():
            keysAndValues.append(i)
            keysAndValues.append(m[i])
def remove(root, key):
    left, right = split(root, key)
    return merge(left, split(right, key + 1)[1])