code: def _create_cat_table(self,data):
          
          table = self.cat_describe['t1_summary'].copy()
          # add the total count of null values across all levels
          isnull = data[self._categorical].isnull().sum().to_frame(name='isnull')
          isnull.index.rename('variable', inplace=True)
          try:
              table = table.join(isnull)
          except TypeError: # if columns form a CategoricalIndex, need to convert to string first
              table.columns = table.columns.astype(str)
              table = table.join(isnull)
  
          # add pval column
          if self._pval and self._pval_adjust:
              table = table.join(self._significance_table[['pval (adjusted)','ptest']])
          elif self._pval:
              table = table.join(self._significance_table[['pval','ptest']])
  
          return table
docs: Create table one for categorical data.
  
          Returns
          ----------
          table : pandas DataFrame
              A table summarising the categorical variables.