code: def test_getitem(stream):
      df = cudf.DataFrame({"x": list(range(10)), "y": [1] * 10})
  
      a = DataFrame(example=df.iloc[:0], stream=stream)
      L = a[a.x > 4].stream.gather().sink_to_list()
  
      a.emit(df.iloc[:5])
      a.emit(df.iloc[5:])
  
      assert len(L) == 2
      assert_eq(cudf.concat(L), df[df.x > 4])
  
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 15 for calling a global function with example usage: test_getitem(stream) without return types