code: def mergeAllLayers(self):
  		
  		start = time.time()
  		while(len(self.layers)>1):
  			self.mergeBottomLayers()
  		print('merge time:'+str(time.time()-start))
  		return self.layers[0]
docs: Merge all the layers together.
  
  		:rtype: The result :py:class:`Layer` object.