parameters: (self, label=None)
docstring: Stop a machine.
          @param label: machine name.
          @raise NotImplementedError: this method is abstract.
docstring_summary: Stop a machine.
docstring_tokens: Stop a machine .
function: def stop(self, label=None):
          """Stop a machine.
          @param label: machine name.
          @raise NotImplementedError: this method is abstract.
          """
          raise NotImplementedError
function_tokens: def stop ( self , label = None ) : raise NotImplementedError