code: def test_merge(self, left, right, expected):
      result = pd.merge(left, right, left_index=True, right_index=True)
      assert result.flags.allows_duplicate_labels is expected
  
imports: import operator
  import numpy
  import pytest
  import pandas
  import pandas._testing
label_desc: Use image node_id 10 for calling the TestPreserves obj's underlying member method code with example usage: obj.test_merge(left, right, expected) without return types