But when I run this I get NameError name alphabeta is not defined error How to solve this

Question

tree = [[[5, 1, 2], [8, -8, -9]], [[9, 4, 5], [-3, 4, 3]]]

root = 0

pruned = 0

def children(branch, depth, aplha, beta):

    global tree

    global root

    global pruned

    i = 0

    for child in branch:

        if type(child) is list:

           (nalpha, nbeta) = children(child, depth + 1, alpha, beta)

           if depth % 2 == 1:

              beta = nalpha if nalpha < beta else beta

           else:

              alpha = nbeta if nbeta > alpha else aplha

           branch[i] = alpha if depth % 2 == 0 else beta

           i += 1

        else:

          if depth % 2 == 0 and alpha < child:

              alpha = child

          if depth % 2 == 1 and beta > child:

             beta = child

          if alpha >= beta:

             pruned += 1

             break

    if depth == root:

       tree = alpha if root == 0 else beta

    return (alpha, beta)

    def alphabeta(in_tree=tree, start=root, upper=-15, lower=15):

      global tree

      global pruned

      global root

      (alpha, beta) = children(tree, start, upper, lower)

    if __name__== "__main__":

      print ("(alpha, beta): ", alpha, beta)

      print ("Result: ", tree)

      print ("Times pruned: ", pruned)

    return (alpha, beta, tree, pruned)

if __name__== "__main__":

      alphabeta(None)