'Raise an exception if the mode in the attribute exchange
arguments does not match what is expected for this class.
@raises NotAXMessage: When there is no mode value in ax_args at all.
@raises AXError: When mode does not match.'

def _checkMode(self, ax_args):

    mode = ax_args.get('mode')
    if (mode != self.mode):
        if (not mode):
            raise NotAXMessage()
        else:
            raise AXError(('Expected    mode    %r;    got    %r' % (self.mode, mode)))
