code: def test_join_with_len0(self, target_source):
      # nothing to merge
      target, source = target_source
      merged = target.join(source.reindex([]), on="C")
      for col in source:
          assert col in merged
          assert merged[col].isna().all()
  
      merged2 = target.join(source.reindex([]), on="C", how="inner")
      tm.assert_index_equal(merged2.columns, merged.columns)
      assert len(merged2) == 0
  
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 16 for calling the TestJoin obj's underlying member method code with example usage: obj.test_join_with_len0(target_source) without return types