code: def Open(self):
      
      if not self._filename:
        raise ValueError('Missing filename.')
  
      if os.path.isfile(self._filename):
        raise IOError((
            'Unable to use an already existing file for output '
            '[{0:s}]').format(self._filename))
  
      options = {
          'constant_memory': True,
          'strings_to_urls': False,
          'strings_to_formulas': False,
          'default_date_format': self._timestamp_format}
      self._workbook = xlsxwriter.Workbook(self._filename, options)
      self._sheet = self._workbook.add_worksheet('Sheet')
      self._current_row = 0
docs: Creates a new workbook.
  
      Raises:
        IOError: if the specified output file already exists.
        OSError: if the specified output file already exists.
        ValueError: if the filename is not set.