code: def test_labels_lists():
      p = ggplot(data, aes(x=[1, 2, 3], y=[1, 2, 3])) + geom_col()
      assert p.labels.x is None
      assert p.labels.y is None
  
file_path: plotnine/tests/test_aes.py
imports: import numpy
  import pandas
  from plotnine import aes, after_stat, geom_col, geom_crossbar, geom_point, ggplot, scale_x_log10, scale_y_log10, stage, stat_bin_2d, stat_ecdf, stat_function
  from plotnine.mapping.aes import make_labels
label_desc: Use image node_id 4 for calling a global function with example usage: test_labels_lists() without return types