code: def test_plt_overlay_with_bands():
      m = 200
      x = np.array(list(range(m)) * m) / (1.0 * m)
      x = x * 2 * math.pi
      z = []
      for u in range(m):
          z = z + [u] * m
      y = np.sin(x) + np.random.normal(0, 1, len(x))
      df = pd.DataFrame({"x": x, "y": y, "z": z})
  
      x_col = "x"
      y_col = "y"
      split_col = "z"
  
      plt_overlay_with_bands(
          df=df,
          x_col=x_col,
          y_col=y_col,
          split_col=split_col,
          perc=[25, 75],
          overlay_color="black",
          agg_col_colors=None,
          plt_title=None,
      )
  
file_path: greykite/greykite/tests/common/viz/test_timeseries_plotting_mpl.py
imports: import datetime
  import math
  from functools import partial
  import matplotlib
  import numpy
  import pandas
  import scipy.stats
  from greykite.common.viz.timeseries_plotting_mpl import plt_compare_timeseries
  from greykite.common.viz.timeseries_plotting_mpl import plt_longterm_ts_agg
  from greykite.common.viz.timeseries_plotting_mpl import plt_overlay_long_df
  from greykite.common.viz.timeseries_plotting_mpl import plt_overlay_with_bands
label_desc: Use image node_id 3 for calling a global function with example usage: test_plt_overlay_with_bands() without return types