code: def test_labels_series():
      p = ggplot(data, aes(x=data.x, y=data.y)) + geom_col()
      assert p.labels.x == "x"
      assert p.labels.y == "y"
  
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 3 for calling a global function with example usage: test_labels_series() without return types