code: def stream(request, client):
      if request.param == "core":
          return Stream()
      else:
          return DaskStream()
  
imports: import json
  import operator
  import numpy
  import pandas
  import pytest
  from dask.dataframe.utils import assert_eq
  from distributed import Client
  from streamz import Stream
  from streamz.dask import DaskStream
  from streamz.dataframe import Aggregation, DataFrame, DataFrames, Series
label_desc: Use image node_id 2 for calling a global function with example usage: stream(request, client) and returns: Stream, DaskStream