code: def _check_stringify_year_column(self, column_index):
          '''
          Same as _check_stringify_year_row but for columns.
          '''
          table_column = TableTranspose(self.table)[column_index]
          # State trackers
          prior_year = None
          for row_index in range(self.start[0]+1, self.end[0]):
              current_year = table_column[row_index]
              if not self._check_years(current_year, prior_year):
                  return
              # Only copy when we see a non-empty entry
              if current_year:
                  prior_year = current_year
  
          # If we have a title of years, convert them to strings
          self._stringify_column(column_indexf _check_stringify_year_column(self, column_index):
          '''
          Same as _check_stringify_year_row but for columns.
          '''
          table_column = TableTranspose(self.table)[column_index]
          # State trackers
          prior_year = None
          for row_index in range(self.start[0]+1, self.end[0]):
              current_year = table_column[row_index]
              if not self._check_years(current_year, prior_year):
                  return
              # Only copy when we see a non-empty entry
              if current_year:
                  prior_year = current_year
  
          # If we have a title of years, convert them to strings
          self._stringify_column(column_index)
docs: Same as _check_stringify_year_row but for columns.