tryton button test

	state = fields.Selection([
		('cancel', 'Canceled'),
		], 'states', readonly=True)

	@classmethod
	def __setup__(cls):
		super(Optar_Monitoring, cls).__setup__()

		cls._transitions |= set((
						('cancel', 'Canceled'),
											))
		cls._buttons.update({
							'cancel': {
							}})


	@classmethod
	@ModelView.button
	@Workflow.transition('cancel')
	def cancel(cls, monitor):
		print "testing"

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XML PART
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                   <button name="cancel" string="_Cancel"
                        icon="tryton-cancel"/>