new_contents: import os
  
  import pytest
  
  import hetio.readwrite
  from hetio.pathtools import paths_between, DWPC
  
  directory = os.path.dirname(os.path.abspath(__file__))
  
  
  def test_disease_gene_example_dwpc():
      """
      Test the DWPC computation from
      https://doi.org/10.1371/journal.pcbi.1004259.g002
      """
      path = os.path.join(directory, 'data', 'disease-gene-example-graph.json')
      graph = hetio.readwrite.read_graph(path)
      metagraph = graph.metagraph
  
      # Define traversal
      metapath = metagraph.metapath_from_abbrev('GiGaD')
      source_id = 'Gene', 'IRF1'
      target_id = 'Disease', 'Multiple Sclerosis'
  
      # Extract paths
      paths = paths_between(graph, source_id, target_id, metapath)
      assert len(paths) == 3
  
      # Test degree-weighted path count
      dwpc = DWPC(paths, damping_exponent=0.5)
      assert dwpc == pytest.approx(0.25 + 0.25 + 32**-0.5)
  
subject: Add PC / DWPC test