class_docstr: Test remove digits.
class_docstr_tok: ["Test","remove","digits","."]
code: def test_has_content(self):
      s = pd.Series(["c", np.nan, "\t\n", " ", "", "has content", None])
      s_true = pd.Series(
          [True, False, False, False, False, True, False]
      )
      self.assertEqual(preprocessing.has_content(s), s_true)
  
imports: import string
  import pytest
  import pandas
  import numpy
  import doctest
  from texthero import preprocessing, stopwords
  from .None import PandasTestCase
  import warnings
label_desc: Use image node_id 22 for calling the TestPreprocessing obj's underlying member method code with example usage: obj.test_has_content() without return types