code: def test_step_mid():
      data = pd.DataFrame({"x": range(9), "y": range(9)})
      p = (
          ggplot(data, aes("x", "y"))
          + geom_point(size=4)
          + geom_step(direction="mid", size=2)
      )
  
      assert p == "step_mid"
  
file_path: plotnine/tests/test_geom_path_line_step.py
imports: import numpy
  import pandas
  import pytest
  from plotnine import aes, arrow, facet_grid, geom_line, geom_path, geom_point, geom_step, ggplot
  from plotnine.exceptions import PlotnineWarning
label_desc: Use image node_id 5 for calling a global function with example usage: test_step_mid() without return types