code: def test_merge_combinations(
      request,
      how,
      sort,
      on_index,
      left_unique,
      left_monotonic,
      right_unique,
      right_monotonic,
  ):
      request.applymarker(
          pytest.mark.xfail(
              condition=how == "outer"
              and on_index
              and left_unique
              and not left_monotonic
              and right_unique
              and not right_monotonic,
              reason="https://github.com/pandas-dev/pandas/issues/55992",
          )
      )
      left = [2, 3]
      if left_unique:
          left.append(4 if left_monotonic else 1)
      else:
          left.append(3 if left_monotonic else 2)
  
      right = [2, 3]
      if right_unique:
          right.append(4 if right_monotonic else 1)
      else:
          right.append(3 if right_monotonic else 2)
  
      left = cudf.DataFrame({"key": left})
      right = cudf.DataFrame({"key": right})
  
      if on_index:
          left = left.set_index("key")
          right = right.set_index("key")
          on_kwargs = {"left_index": True, "right_index": True}
      else:
          on_kwargs = {"on": "key"}
  
      with cudf.option_context("mode.pandas_compatible", True):
          result = cudf.merge(
              left, right, how=how, sort=sort, **on_kwargs
          )
      if on_index:
          left = left.reset_index()
          right = right.reset_index()
  
      if how in ["left", "right", "inner"]:
          if how in ["left", "inner"]:
              expected, other, other_unique = left, right, right_unique
          else:
              expected, other, other_unique = right, left, left_unique
          if how == "inner":
              keep_values = set(left["key"].values_host).intersection(
                  right["key"].values_host
              )
              keep_mask = expected["key"].isin(keep_values)
              expected = expected[keep_mask]
          if sort:
              expected = expected.sort_values("key")
          if not other_unique:
              other_value_counts = other["key"].value_counts()
              repeats = other_value_counts.reindex(
                  expected["key"].values, fill_value=1
              )
              repeats = repeats.astype(np.intp)
              expected = expected["key"].repeat(repeats.values)
              expected = expected.to_frame()
      elif how == "outer":
          if (
              on_index
              and left_unique
              and left["key"].equals(right["key"])
          ):
              expected = cudf.DataFrame({"key": left["key"]})
          else:
              left_counts = left["key"].value_counts()
              right_counts = right["key"].value_counts()
              expected_counts = left_counts.mul(
                  right_counts, fill_value=1
              )
              expected_counts = expected_counts.astype(np.intp)
              expected = expected_counts.index.values_host.repeat(
                  expected_counts.values_host
              )
              expected = cudf.DataFrame({"key": expected})
              expected = expected.sort_values("key")
  
      if on_index:
          expected = expected.set_index("key")
      else:
          expected = expected.reset_index(drop=True)
  
      assert_eq(result, expected)
  
file_path: cudf/python/cudf/cudf/tests/test_join_order.py
imports: import itertools
  import operator
  import string
  from collections import defaultdict
  import numpy
  import pytest
  import cudf
  from cudf.core._compat import PANDAS_GE_220
  from cudf.testing._utils import assert_eq
label_desc: Use image node_id 5 for calling a global function with example usage: test_merge_combinations(request, how, sort, on_index, left_unique, left_monotonic, right_unique, right_monotonic) without return types