code: def test_violinplot(self):
      fig, ax = plt.subplots()
      ax.violinplot(...)
  
imports: import datetime
  import numpy
  import pytest
  import matplotlib.pyplot
  import matplotlib
label_desc: Use image node_id 50 for calling the TestDatetimePlotting obj's underlying member method code with example usage: obj.test_violinplot() without return types