code: def test_streaming_literal_expansion() -> None:
      df = pl.DataFrame(
          {
              "y": ["a", "b"],
              "z": [1, 2],
          }
      )
  
      q = df.lazy().select(
          x=pl.lit("constant"),
          y=pl.col("y"),
          z=pl.col("z"),
      )
  
      assert q.collect(streaming=True).to_dict(as_series=False) == {
          "x": ["constant", "constant"],
          "y": ["a", "b"],
          "z": [1, 2],
      }
      assert q.group_by(["x", "y"]).agg(pl.mean("z")).sort("y").collect(
          streaming=True
      ).to_dict(as_series=False) == {
          "x": ["constant", "constant"],
          "y": ["a", "b"],
          "z": [1.0, 2.0],
      }
      assert q.group_by(["x"]).agg(pl.mean("z")).collect().to_dict(
          as_series=False
      ) == {
          "x": ["constant"],
          "z": [1.5],
      }
  
imports: from __future__ import annotations
  import os
  import tempfile
  import time
  from datetime import date
  from pathlib import Path
  from typing import TYPE_CHECKING, Any
  import numpy
  import pytest
  import polars
  from polars.exceptions import PolarsInefficientMapWarning
  from polars.testing import assert_frame_equal
label_desc: Use image node_id 5 for calling a global function with example usage: test_streaming_literal_expansion() without return types