code: def test_simple_normalize_with_separator(self, deep_nested):
      # GH 14883
      result = json_normalize({"A": {"A": 1, "B": 2}})
      expected = DataFrame([[1, 2]], columns=["A.A", "A.B"])
      tm.assert_frame_equal(result.reindex_like(expected), expected)
  
      result = json_normalize({"A": {"A": 1, "B": 2}}, sep="_")
      expected = DataFrame([[1, 2]], columns=["A_A", "A_B"])
      tm.assert_frame_equal(result.reindex_like(expected), expected)
  
      result = json_normalize({"A": {"A": 1, "B": 2}}, sep="\u03c3")
      expected = DataFrame([[1, 2]], columns=["A\u03c3A", "A\u03c3B"])
      tm.assert_frame_equal(result.reindex_like(expected), expected)
  
      result = json_normalize(
          deep_nested,
          ["states", "cities"],
          meta=["country", ["states", "name"]],
          sep="_",
      )
      expected = Index(
          ["name", "pop", "country", "states_name"]
      ).sort_values()
      assert result.columns.sort_values().equals(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 6 for calling the TestJSONNormalize obj's underlying member method code with example usage: obj.test_simple_normalize_with_separator(deep_nested) without return types