code: def test_join_on_inner(self):
      df = DataFrame({"key": ["a", "a", "d", "b", "b", "c"]})
      df2 = DataFrame({"value": [0, 1]}, index=["a", "b"])
  
      joined = df.join(df2, on="key", how="inner")
  
      expected = df.join(df2, on="key")
      expected = expected[expected["value"].notna()]
      tm.assert_series_equal(joined["key"], expected["key"])
      tm.assert_series_equal(
          joined["value"], expected["value"], check_dtype=False
      )
      tm.assert_index_equal(joined.index, expected.index)
  
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 17 for calling the TestJoin obj's underlying member method code with example usage: obj.test_join_on_inner() without return types