code: def pdf(request):
      np.random.seed(0)
  
      # note that column name "x" is a substring of the groupby key;
      # this gives us coverage for cudf#10829
      pdf = pd.DataFrame(
          {
              "xx": np.random.randint(0, 5, size=10000),
              "x": np.random.normal(size=10000),
              "y": np.random.normal(size=10000),
          }
      )
  
      # insert nulls into dataframe at random
      if request.param == "null":
          pdf = pdf.mask(
              np.random.choice([True, False], size=pdf.shape)
          )
  
      return pdf
  
imports: import numpy
  import pandas
  import pytest
  import dask
  from dask import dataframe
  from dask.utils_test import hlg_layer
  import cudf
  import dask_cudf
  from dask_cudf.groupby import OPTIMIZED_AGGS, _aggs_optimized
label_desc: Use image node_id 2 for calling a global function with example usage: pdf(request) and returns: pdf