code: def _ensure_category_col_is_in_df(self):
      if self._category_col not in self._df:
          self._category_col = "Category"
          while self._category_col in self._df:
              self._category_col = "Category_" + "".join(
                  np.random.choice(string.ascii_letters)
                  for _ in range(5)
              )
          self._df[self._category_col] = ""
  
file_path: scattertext/scattertext/OffsetCorpusFactory.py
imports: import string
  import numpy
  from scattertext.OffsetCorpus import OffsetCorpus
  from scattertext.CSRMatrixTools import CSRMatrixFactory
  from scattertext.indexstore.IndexStore import IndexStore
label_desc: Use image node_id 3 for calling the OffsetCorpusFactory obj's underlying member method code with example usage: obj._ensure_category_col_is_in_df() without return types