code: def bench_groupby(benchmark, dataframe, num_key_cols):
      benchmark(
          dataframe.groupby, by=list(dataframe.columns[:num_key_cols])
      )
  
imports: import string
  import numpy
  import pytest
  import pytest_cases
  from config import cudf, cupy
  from utils import benchmark_with_object
label_desc: Use image node_id 11 for calling a global function with example usage: bench_groupby(benchmark, dataframe, num_key_cols) without return types