code: ## create graph
  from pyvis.network import Network
  import llama_index.core
  from llama_index.core import StorageContext, load_index_from_storage
  
  storage_context = StorageContext.from_defaults(persist_dir="math_index_persist")
  index = load_index_from_storage(storage_context)
  # retriever = llama_index.core.indices.knowledge_graph.KGTableRetriever(index)
  
  g = index.get_networkx_graph()
  net = Network(notebook=True, cdn_resources="in_line", directed=True)
  net.from_nx(g)
  net.show("example.html")
  
apis: llama_index.core.StorageContext.from_defaults llama_index.core.load_index_from_storage
extract_api: [((162, 224), 'llama_index.core.StorageContext.from_defaults', 'StorageContext.from_defaults', ([], {'persist_dir': '"""math_index_persist"""'}), "(persist_dir='math_index_persist')\n", (190, 224), False, 'from llama_index.core import StorageContext, load_index_from_storage\n'), ((233, 273), 'llama_index.core.load_index_from_storage', 'load_index_from_storage', (['storage_context'], {}), '(storage_context)\n', (256, 273), False, 'from llama_index.core import StorageContext, load_index_from_storage\n'), ((391, 453), 'pyvis.network.Network', 'Network', ([], {'notebook': '(True)', 'cdn_resources': '"""in_line"""', 'directed': '(True)'}), "(notebook=True, cdn_resources='in_line', directed=True)\n", (398, 453), False, 'from pyvis.network import Network\n')]