code: def test_sign_plot(self):
      x = np.array([[1, 1, 1], [1, 1, 0], [1, 0, 1]])
      a = splt.sign_plot(x, flat=True, labels=False)
      with self.assertRaises(ValueError):
          splt.sign_plot(x.astype(float), flat=True, labels=False)
      self.assertTrue(isinstance(a, ma._axes.Axes))
  
imports: import os
  import sys
  import unittest
  import matplotlib
  import scikit_posthocs._posthocs
  import scikit_posthocs._omnibus
  import scikit_posthocs._outliers
  import scikit_posthocs._plotting
  import scikit_posthocs._global
  import seaborn
  import numpy
  import matplotlib.axes
  from pandas import DataFrame, Series
label_desc: Use image node_id 5 for calling the TestPosthocs obj's underlying member method code with example usage: obj.test_sign_plot() without return types