code: def test_normalize_with_multichar_separator(self):
      # GH #43831
      data = {"a": [1, 2], "b": {"b_1": 2, "b_2": (3, 4)}}
      result = json_normalize(data, sep="__")
      expected = DataFrame(
          [[[1, 2], 2, (3, 4)]], columns=["a", "b__b_1", "b__b_2"]
      )
      tm.assert_frame_equal(result, expected)
  
imports: import json
  import numpy
  import pytest
  from pandas import DataFrame, Index, Series, json_normalize
  import pandas._testing
  from pandas.io.json._normalize import nested_to_record
label_desc: Use image node_id 7 for calling the TestJSONNormalize obj's underlying member method code with example usage: obj.test_normalize_with_multichar_separator() without return types