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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 mergeAllLayers(self):
 		""" 		Merge all the layers together. 		:rtype: The result :py:class:`Layer` object. 		"""

		start = time.time()
		while(len(self.layers)>1):
			self.mergeBottomLayers()
		print('merge time:'+str(time.time()-start))
		return self.layers[0]