code: def test_attribute_mixing_dict_undirected(self):
      d = nx.attribute_mixing_dict(self.G, "fish")
      d_result = {
          "one": {"one": 2, "red": 1},
          "two": {"two": 2, "blue": 1},
          "red": {"one": 1},
          "blue": {"two": 1},
      }
      assert d == d_result
  
imports: import pytest
  import networkx
  from .base_test import BaseTestAttributeMixing, BaseTestDegreeMixing
label_desc: Use image node_id 1 for calling the TestAttributeMixingDict obj's underlying member method code with example usage: obj.test_attribute_mixing_dict_undirected() without return types