code: def test_dtype(stream):
      df = cudf.DataFrame({"x": [1, 2, 3], "y": [4, 5, 6]})
      sdf = DataFrame(example=df, stream=stream)
  
      assert str(sdf.dtypes) == str(df.dtypes)
      assert sdf.x.dtype == df.x.dtype
      assert sdf.index.dtype == df.index.dtype
  
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 4 for calling a global function with example usage: test_dtype(stream) without return types