code: def test_giniindex(self):
      name = "giniindex"
      Metric = metrics_dict[name](config)
      self.assertEqual(
          Metric.get_gini(item_matrix, num_items),
          (
              (-7) * 0
              + (-5) * 1
              + (-3) * 1
              + (-1) * 2
              + 1 * 2
              + 3 * 2
              + 5 * 3
              + 7 * 4
          )
          / (8 * (3 * 5)),
      )
  
file_path: RecBole/tests/metrics/test_topk_metrics.py
imports: import os
  import sys
  import unittest
  import numpy
  from recbole.config import Config
  from recbole.evaluator.register import metrics_dict
label_desc: Use image node_id 9 for calling the TestTopKMetrics obj's underlying member method code with example usage: obj.test_giniindex() without return types