diff --git a/third_party/paddle_audio/frontend/kaldi.py b/third_party/paddle_audio/frontend/kaldi.py
index 154148081..dc3e5cd69 100644
--- a/third_party/paddle_audio/frontend/kaldi.py
+++ b/third_party/paddle_audio/frontend/kaldi.py
@@ -6,7 +6,8 @@ from paddle import nn
 from paddle.nn import functional as F
 import soundfile as sf
 
-from .common import get_window, dft_matrix
+from .common import get_window
+from .common import dft_matrix
 
 
 def read(wavpath:str, sr:int = None, start=0, stop=None, dtype='int16', always_2d=True)->Tuple[int, np.ndarray]:
@@ -27,6 +28,14 @@ def read(wavpath:str, sr:int = None, start=0, stop=None, dtype='int16', always_2
 
 
 def write(wavpath:str, wav:np.ndarray, sr:int, dtype='PCM_16'):
+    """write wav file.
+
+    Args:
+        wavpath (str): file path to save.
+        wav (np.ndarray): wav data.
+        sr (int): data samplerate.
+        dtype (str, optional): wav bit format. Defaults to 'PCM_16'.
+    """
     sf.write(wavpath, wav, sr, subtype=dtype)
 
 
diff --git a/third_party/paddle_audio/frontend/kaldi_test.py b/third_party/paddle_audio/frontend/kaldi_test.py
index 2f729244a..34ff413c5 100644
--- a/third_party/paddle_audio/frontend/kaldi_test.py
+++ b/third_party/paddle_audio/frontend/kaldi_test.py
@@ -13,7 +13,6 @@ from scipy.fftpack import dct
 
 from third_party.paddle_audio.frontend import kaldi
 
-
 def round_half_up(number):
     return int(decimal.Decimal(number).quantize(decimal.Decimal('1'), rounding=decimal.ROUND_HALF_UP))