@fields.depends('available')
	def on_change_renter(self, name=None):
		if self.renter:
                        self.available = False
		else:
                        self.available = True

	@fields.depends('renter')
	def on_change_available(self):
		if self.available:
			self.renter = 'Chris'
		else:
			self.renter = ''