class_docstr: This class represents a directed graph using adjacency lists
class_docstr_tok: ["This","class","represents","a","directed","graph","using","adjacency","lists"]
docstr: Adds a directed edge to the graph
docstr_tok: ["Adds","a","directed","edge","to","the","graph"]
code: def add_edge(self, source, target):
      """
      Adds a directed edge to the graph
      """
      if source in self.graph:
          self.graph[source].append(target)
      else:
          self.graph[source] = [target]
  
label_desc: Use image node_id 2 for calling the Graph obj's underlying member method code with example usage: obj.add_edge(source, target) without return types