code: def build_compressed_graph(self):
      compressed_matrix = [
          ("1", "BC"),
          ("2", ["ABC"]),
          ("3", ["A", "B", "6"]),
          ("4", ["ABC"]),
          ("5", "AB"),
          ("6", ["5"]),
          ("A", ["6"]),
          ("ABC", "ABC"),
      ]
      compressed_graph = nx.DiGraph()
      for source, targets in compressed_matrix:
          for target in targets:
              compressed_graph.add_edge(source, target)
      return compressed_graph
  
imports: import pytest
  import networkx
label_desc: Use image node_id 2 for calling the TestDirectedDedensification obj's underlying member method code with example usage: obj.build_compressed_graph() and returns: compressed_graph