code: def set_mode(self, value=None, default=False, disable=False):
          
          if not default and not disable:
              if value not in ['mstp', 'none']:
                  raise ValueError("Specified value must be one of "
                                   "'mstp', 'none'")
          cmds = self.command_builder('spanning-tree mode', value=value,
                                      default=default, disable=disable)
          return self.configure(cmds)
docs: Configures the global spanning-tree mode
  
          Note:
              This configuration parameter is not defaultable
  
          Args:
              value (string): The value to configure the global spanning-tree
                  mode of operation.  Valid values include 'mstp', 'none'
              default (bool): Set the global spanning-tree mode to default.
              disable (bool): Negate the global spanning-tree mode.
  
          Returns:
              True if the configuration operation succeeds otherwise False
  
          Raises:
              ValueError if the value is not in the accepted range