code: def compute(self, rank_above, negative_num):
      del negative_num
      denominator = 0.0
      for i in range(len(rank_above)):
          denominator += 1.0 / log(i + 2, 2)
  
      results = np.zeros(len(self._ndcg_at))
      for r in rank_above:
          tmp = 1.0 / log(r + 2, 2)
          results[r < self._ndcg_at] += tmp
  
      return results / denominator
  
imports: import numpy
  from math import log
  from openrec.tf1.utils.evaluators import Evaluator
label_desc: Use image node_id 2 for calling the NDCG obj's underlying member method code with example usage: obj.compute(rank_above, negative_num) and returns: unknown