code: def test_arrow_facets():
      data = pd.DataFrame(
          {
              "x": [1, 3, 2, 4],
              "y": [10, 9, 10, 9],
              "z": ["a", "a", "b", "b"],
          }
      )
  
      p = (
          ggplot(data, aes("x", "y"))
          + geom_path(size=2, arrow=arrow(length=0.25))
          + facet_grid("~ z")
      )
      assert p == "arrow_facets"
  
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 3 for calling a global function with example usage: test_arrow_facets() without return types