docs: def init_graph(self):
          """
          Initialize graph
          Load all nodes and set dependencies.
  
          To avoid errors about missing nodes all nodes get loaded first before
          setting the dependencies.
          """
          self._graph = Graph()
  
          # First add all nodes
          for key in self.loader.disk_fixtures.keys():
              self.graph.add_node(key)
  
          # Then set dependencies
          for key, fixture in self.loader.disk_fixtures.items():
              for dependency in fixture.dependencies:
                  self.graph.add_dependency(key, dependency)