code: def col_values(self, col, value_render_option='FORMATTED_VALUE'):
          
  
          start_label = rowcol_to_a1(1, col)
          range_label = '%s!%s:%s' % (self.title, start_label, start_label[:-1])
  
          data = self.spreadsheet.values_get(
              range_label,
              params={
                  'valueRenderOption': value_render_option,
                  'majorDimension': 'COLUMNS'
              }
          )
  
          try:
              return data['values'][0]
          except KeyError:
              return []
docs: Returns a list of all values in column `col`.
  
          Empty cells in this list will be rendered as :const:`None`.
  
          :param col: Column number.
          :type col: int
          :param value_render_option: (optional) Determines how values should be
                                      rendered in the the output. See
                                      `ValueRenderOption`_ in the Sheets API.
          :type value_render_option: str
  
          .. _ValueRenderOption: https://developers.google.com/sheets/api/reference/rest/v4/ValueRenderOption