class_docstr: Class for computing metrics based on a single
  :obj:`~aif360.datasets.RegressionDataset`.
code: def _dcg(self, scores):
      logs = np.log2(np.arange(2, len(scores) + 2))
      z = np.sum(scores / logs)
      return z
  
file_path: AIF360/aif360/metrics/regression_metric.py
imports: import numpy
  from aif360.metrics import DatasetMetric
  from aif360.datasets import RegressionDataset
label_desc: Use image node_id 4 for calling the RegressionDatasetMetric obj's underlying member method code with example usage: obj._dcg(scores) and returns: z