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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 display(self, buffer = None):
 """! \~english Write buffer to physical display. @param buffer: Data to display，If <b>None</b> mean will use self._buffer data to display \~chinese 将缓冲区写入物理显示屏。 @param buffer: 要显示的数据，如果是 <b>None</b>(默认) 将把 self._buffer 数据写入物理显示屏 """

        if buffer != None:
            self._display_buffer( buffer )
        else:
            self._display_buffer( self._buffer )