code: def test_polar_gridlines():
      fig = plt.figure()
      ax = fig.add_subplot(polar=True)
      # make all major grid lines lighter, only x grid lines set in 2.1.0
      ax.grid(alpha=0.2)
      # hide y tick labels, no effect in 2.1.0
      plt.setp(ax.yaxis.get_ticklabels(), visible=False)
      fig.canvas.draw()
      assert ax.xaxis.majorTicks[0].gridline.get_alpha() == 0.2
      assert ax.yaxis.majorTicks[0].gridline.get_alpha() == 0.2
  
imports: import numpy
  from numpy.testing import assert_allclose
  import pytest
  import matplotlib
  from matplotlib import pyplot
  from matplotlib.testing.decorators import image_comparison, check_figures_equal
label_desc: Use image node_id 22 for calling a global function with example usage: test_polar_gridlines() without return types