code: def WriteHeader(self):
      
      self._column_widths = {}
      bold = self._workbook.add_format({'bold': True})
      bold.set_align('center')
      for index, field_name in enumerate(self._fields):
        self._sheet.write(self._current_row, index, field_name, bold)
        self._column_widths[index] = len(field_name) + 2
      self._current_row += 1
      self._sheet.autofilter(0, len(self._fields) - 1, 0, 0)
      self._sheet.freeze_panes(1, 0)
docs: Writes the header to the spreadsheet.