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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def button_number(self):
 		"""The button number that triggered this event, starting at 0. 		For events that are not of type 		:attr:`~libinput.constant.Event.TABLET_PAD_BUTTON`, 		this property raises :exc:`AttributeError`. 		Note that the number returned is a generic sequential button number 		and not a semantic button code as defined in ``linux/input.h``. 		See `Tablet pad button numbers`_ for more details. 		Returns: 			int: The button triggering this event. 		Raises: 			AttributeError 		"""


		if self.type != EventType.TABLET_PAD_BUTTON:
			raise AttributeError(_wrong_prop.format(self.type))
		return self._libinput.libinput_event_tablet_pad_get_button_number(
			self._handle)