code: def copy_graph(subject, existing_graph):
      
      new_graph = rdflib.Graph()
      for predicate, object_ in existing_graph.predicate_objects():
          new_graph.add((subject, predicate, object_))
      return new_graph
docs: Function takes a subject and an existing graph, returns a new graph with
      all predicate and objects of the existing graph copied to the new_graph with
      subject as the new subject
  
      Args:
          subject(rdflib.URIRef): A URIRef subject
          existing_graph(rdflib.Graph): A rdflib.Graph
  
      Returns:
          rdflib.Graph