code: def test_merge_raises(self):
      a = pd.DataFrame(
          {"A": [0, 1, 2]}, index=["a", "b", "c"]
      ).set_flags(allows_duplicate_labels=False)
      b = pd.DataFrame({"B": [0, 1, 2]}, index=["a", "b", "b"])
      msg = "Index has duplicates."
      with pytest.raises(pd.errors.DuplicateLabelError, match=msg):
          pd.merge(a, b, left_index=True, right_index=True)
  
imports: import operator
  import numpy
  import pytest
  import pandas
  import pandas._testing
label_desc: Use image node_id 6 for calling the TestRaises obj's underlying member method code with example usage: obj.test_merge_raises() without return types