class_docstr: PosTag (Part of Speech Tagging Visualizer) Tests
docstr: Assert no errors occur when the visualizer is run on both stack and
  frequency mode
docstr_tok: ["Assert","no","errors","occur","when","the","visualizer","is","run","on","both","stack","and","frequency","mode"]
code: def test_stack_frequency_mode(self):
      """
      Assert no errors occur when the visualizer is run on both stack and
      frequency mode
      """
      check_nltk_data()
  
      _, ax = plt.subplots()
      tagged_docs = list(get_tagged_docs(sonnets))
  
      visualizer = PosTagVisualizer(stack=True, frequency=True, ax=ax)
      visualizer.fit(tagged_docs, y=["a", "b", "c"])
      visualizer.ax.grid(False)
  
      # Sorted tags i.e predetermined order
      sorted_tags = [
          "noun",
          "adjective",
          "punctuation",
          "verb",
          "preposition",
          "determiner",
          "adverb",
          "conjunction",
          "pronoun",
          "wh- word",
          "modal",
          "infinitive",
          "possessive",
          "other",
          "symbol",
          "existential",
          "digit",
          "non-English",
          "interjection",
          "list",
      ]
  
      # Extract tick labels from the plot
      ticks_ax = [tick.get_text() for tick in ax.xaxis.get_ticklabels()]
  
      # Assert that ticks are set properly
      assert ticks_ax == sorted_tags
  
      self.assert_images_similar(ax=ax)
  
imports: import pytest
  import matplotlib.pyplot
  from tests.base import VisualTestCase
  from tests.base import IS_WINDOWS_OR_CONDA
  from yellowbrick.text.postag import *
  from yellowbrick.exceptions import YellowbrickValueError
label_desc: Use image node_id 11 for calling the TestPosTag obj's underlying member method code with example usage: obj.test_stack_frequency_mode() without return types