def __init__(self, indir=None): """ Initialize the instance. @indir (string) The directry path containing CT iamages. """ self.stack = None self.mask = None self.shape = None self.outdir = None self.peak_air = None self.peak_soil = None self.diff = None if indir is not None: self.loadStack(indir) else: self.indir = None def loadStack(self, indir): """ Load the CT images. @indir (string) The directry path containing the CT iamages. """ self.indir = indir files = glob.glob(os.path.join(self.indir, '*.*')) files = [f for f in files if f.endswith('.cb')] #// '.cb' is the extension of the CT iamges generated with Shimazdu X-ray CT system if len(files) == 0: raise Exception('Stack loading failed.') files.sort() print('Stack loading: {}'.format(self.indir)) self.stack = [io.imread(f) for f in tqdm.tqdm(files)] self.stack = np.asarray(self.stack, dtype=np.uint16) #// '.cb' files is the 16-bit grayscale images self.shape = self.stack.shape return def checkStack(self): """ Check whether the CT images was loaded. """ if self.stack is None: raise Exception('The CT images not loaded.') def checkMask(self): """ Check whether the CT mask was computed. """ if self.mask is None: raise Exception('The mask not computed.') def saveStack(self, outdir): """ Save the processed images. @outdir (string) The directry path where self.stack will be saved. """ self.checkStack() self.outdir = outdir if not os.path.isdir(self.outdir): os.makedirs(self.outdir) print('Stack saving: {}'.format(self.outdir)) for i, img in enumerate(tqdm.tqdm(self.stack)): img = exposure.rescale_intensity(img, in_range=(0,255), out_range=(0,255)).astype(np.uint8) out = os.path.join(self.outdir, 'img%s.png' % str(i).zfill(4)) io.imsave(out, img) return对于每一行代码，请详细解释一下

该代码是一个Python类的初始化函数及其中一个方法。当创建该类的实例时（使用类名加括号），该初始化函数将被调用，并在其中设置类的一些属性。indir是初始化函数的参数，如果传入，则会调用loadStack方法来读取中心切片CT图像的文件路径。loadStack方法同样需要传入一个indir参数，并使用glob模块获取路径下所有后缀为.cb的文件。