code: def test_graph_base(fake_writer):
      nodes = [
          {"name": "结点1", "symbolSize": 10},
          {"name": "结点2", "symbolSize": 20},
          {"name": "结点3", "symbolSize": 30},
          {"name": "结点4", "symbolSize": 40},
      ]
      links = []
      for i in nodes:
          for j in nodes:
              links.append(
                  {"source": i.get("name"), "target": j.get("name")}
              )
      c = Graph().add("", nodes, links, repulsion=8000)
      c.render()
      _, content = fake_writer.call_args[0]
      assert_equal(c.theme, "white")
      assert_equal(c.renderer, "canvas")
  
file_path: pyecharts/test/test_graph.py
imports: import os
  import json
  from unittest.mock import patch
  from nose.tools import assert_equal, assert_in
  from pyecharts import options
  from pyecharts.charts import Graph
label_desc: Use image node_id 1 for calling a global function with example usage: test_graph_base(fake_writer) without return types