code: def test_param_expr():
      height_var = alt.param(name="height")
      inner_var = height_var / 2
      tick_var = (3 * height_var) / 4
  
      height_str = height_var._to_expr()
      inner_str = inner_var._to_expr()
      tick_str = tick_var._to_expr()
  
      assert height_str == "height"
      assert inner_str == "(height / 2)"
      assert tick_str == "((3 * height) / 4)"
  
      data = pd.DataFrame(
          {"r1": [310, 0], "r2": [270, 0], "r3": [125, 225]}
      )
  
      c1 = alt.Chart(data).mark_bar(size=height_var).encode(x="r1")
  
      c2 = alt.Chart(data).mark_bar(size=inner_var).encode(x="r2")
  
      c3 = alt.Chart(data).mark_tick(size=tick_var).encode(x="r3")
  
      c = (c1 + c2 + c3).add_params(height_var)
  
      dct = c.to_dict()
      expr_set = {d["mark"]["size"]["expr"] for d in dct["layer"]}
  
      assert "height" in expr_set
      assert "(height / 2)" in expr_set
      assert "((3 * height) / 4)" in expr_set
  
file_path: altair/tests/vegalite/v5/test_params.py
imports: import pandas
  import warnings
  import pytest
  import re
  import altair.vegalite.v5
label_desc: Use image node_id 2 for calling a global function with example usage: test_param_expr() without return types