我正在尝试使用示例脚本found here来绘制nexrad 2级文件from here，但出现无效数据错误。

Traceback (most recent call last):
   File "F:\z0sh\py\NEXRAD_Level_2_File.py",line 28,in <module>
    f = Level2File( filename )
  File "F:\z0bin\python\py38\lib\site-packages\metpy\io\nexrad.py",line 177,in __init__
    self._buffer = IOBuffer.fromfile(fobj)
  File "F:\z0bin\python\py38\lib\site-packages\metpy\io\_tools.py",line 179,in fromfile
    return cls(fobj.read())
  File "bz2.py",line 182,in read
  File "_compression.py",line 103,in read
OSError: Invalid data stream