code: def check_nltk_data():
      """
      Returns True if NLTK data has been downloaded, False otherwise
      """
      try:
          nltk.data.find("corpora/treebank")
          return True
      except LookupError:
          pytest.xfail(
              "error occured because nltk postag data is not available"
          )
  
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 1 for calling a global function with example usage: check_nltk_data() and returns: True