code: def test_stackplot(self):
      mpl.rcParams["date.converter"] = "concise"
      N = 10
      stacked_nums = np.tile(np.arange(1, N), (4, 1))
      dates = np.array(
          [datetime.datetime(2020 + i, 1, 1) for i in range(N - 1)]
      )
  
      fig, ax = plt.subplots(layout="constrained")
      ax.stackplot(dates, stacked_nums)
  
imports: import datetime
  import numpy
  import pytest
  import matplotlib.pyplot
  import matplotlib
label_desc: Use image node_id 39 for calling the TestDatetimePlotting obj's underlying member method code with example usage: obj.test_stackplot() without return types