docs: def execute_update(self, update, safe=False):
  		''' Execute an update expression.  Should generally only be called implicitly.
  		'''
  
  		# safe = self.safe
  		# if update.safe is not None:
  		#     safe = remove.safe
  
  		assert len(update.update_data) > 0
  		self.queue.append(UpdateOp(self.transaction_id, self, update.query.type, safe, update))
  		if self.autoflush:
  			return self.flush()