code: def test_compress_group_combinations(self):
      # ~ 40000000 possible unique groups
      key1 = [str(i) for i in range(10000)]
      key1 = np.tile(key1, 2)
      key2 = key1[::-1]
  
      df = DataFrame(
          {
              "key1": key1,
              "key2": key2,
              "value1": np.random.default_rng(2).standard_normal(20000),
          }
      )
  
      df2 = DataFrame(
          {
              "key1": key1[::2],
              "key2": key2[::2],
              "value2": np.random.default_rng(2).standard_normal(10000),
          }
      )
  
      # just to hit the label compression code path
      merge(df, df2, how="outer")
  
imports: import numpy
  import pytest
  import pandas.util._test_decorators
  import pandas
  from pandas import DataFrame, Index, MultiIndex, RangeIndex, Series, Timestamp, option_context
  import pandas._testing
  from pandas.core.reshape.concat import concat
  from pandas.core.reshape.merge import merge
label_desc: Use image node_id 5 for calling the TestMergeMulti obj's underlying member method code with example usage: obj.test_compress_group_combinations() without return types