class_docstr: Test various aspects of the directed GrapohSAGE node generator, with the focus
  on the sampled neighbourhoods and the extracted features.
code: def test_weighted(self):
      g, checker = weighted_tree(is_directed=True)
  
      gen = DirectedGraphSAGENodeGenerator(
          g, 7, [5, 3], [5, 3], weighted=True
      )
      samples = gen.flow([0] * 10)
  
      checker(
          node_id
          for array in samples[0][0]
          for node_id in array.ravel()
      )
  
file_path: stellargraph/tests/mapper/test_directed_node_generator.py
imports: import networkx
  import pandas
  from stellargraph.mapper import DirectedGraphSAGENodeGenerator
  from stellargraph.core.graph import StellarDiGraph
  from ..test_utils.graphs import weighted_tree
label_desc: Use image node_id 4 for calling the TestDirectedNodeGenerator obj's underlying member method code with example usage: obj.test_weighted() without return types