code: def test_matshow(self):
      a = np.diag(range(5))
      dt_start = datetime.datetime(1980, 4, 15)
      dt_end = datetime.datetime(2020, 11, 11)
      extent = (dt_start, dt_end, dt_start, dt_end)
      fig, ax = plt.subplots()
      ax.matshow(a, extent=extent)
      for label in ax.get_xticklabels():
          label.set_rotation(90)
  
imports: import datetime
  import numpy
  import pytest
  import matplotlib.pyplot
  import matplotlib
label_desc: Use image node_id 29 for calling the TestDatetimePlotting obj's underlying member method code with example usage: obj.test_matshow() without return types