code: def _groupby_op(ddf):
      return ddf.groupby("name").agg({"x": "mean"})
  
imports: from __future__ import annotations
  import os
  import pytest
  import sys
  from operator import getitem
  from distributed import Client, SchedulerPlugin
  from distributed.utils_test import cluster, loop
  from dask.highlevelgraph import HighLevelGraph
  from dask.layers import ArrayChunkShapeDep, ArraySliceDep, fractional_slice
label_desc: Use image node_id 14 for calling a global function with example usage: _groupby_op(ddf) and returns: ddf