code: def test_join_datetime_string(self):
      # GH 5647
      dfa = DataFrame(
          [
              ["2012-08-02", "L", 10],
              ["2012-08-02", "J", 15],
              ["2013-04-06", "L", 20],
              ["2013-04-06", "J", 25],
          ],
          columns=["x", "y", "a"],
      )
      dfa["x"] = pd.to_datetime(dfa["x"]).astype("M8[ns]")
      dfb = DataFrame(
          [["2012-08-02", "J", 1], ["2013-04-06", "L", 2]],
          columns=["x", "y", "z"],
          index=[2, 4],
      )
      dfb["x"] = pd.to_datetime(dfb["x"]).astype("M8[ns]")
      result = dfb.join(dfa.set_index(["x", "y"]), on=["x", "y"])
      expected = DataFrame(
          [
              [Timestamp("2012-08-02 00:00:00"), "J", 1, 15],
              [Timestamp("2013-04-06 00:00:00"), "L", 2, 20],
          ],
          index=[2, 4],
          columns=["x", "y", "z", "a"],
      )
      expected["x"] = expected["x"].astype("M8[ns]")
      tm.assert_frame_equal(result, expected)
  
imports: import re
  import numpy
  import pytest
  import pandas.util._test_decorators
  import pandas
  from pandas import Categorical, DataFrame, Index, MultiIndex, Series, Timestamp, bdate_range, concat, merge, option_context
  import pandas._testing
label_desc: Use image node_id 39 for calling the TestJoin obj's underlying member method code with example usage: obj.test_join_datetime_string() without return types