PIL中分离通道发生“AttributeError: 'NoneType' object has no attribute 'bands'”

def split(self):
"Split image into bands"
self.load()    //增加这一行
if self.im.bands == 1:
ims = [self.copy()]
else:
ims = []
#self.load()   //注释这一行
for i in range(self.im.bands):
ims.append(self._new(self.im.getband(i)))
return tuple(ims)