code: def _InitializeGraph(self, os_name, artifact_list):
      
      dependencies = artifact_registry.REGISTRY.SearchDependencies(
          os_name, artifact_list)
      artifact_names, attribute_names = dependencies
  
      self._AddAttributeNodes(attribute_names)
      self._AddArtifactNodesAndEdges(artifact_names)
docs: Creates the nodes and directed edges of the dependency graph.
  
      Args:
        os_name: String specifying the OS name.
        artifact_list: List of requested artifact names.