diff --git a/deepspeech/exps/deepspeech2/model.py b/deepspeech/exps/deepspeech2/model.py
index c414ff130..3db144341 100644
--- a/deepspeech/exps/deepspeech2/model.py
+++ b/deepspeech/exps/deepspeech2/model.py
@@ -31,12 +31,8 @@ from deepspeech.training import Trainer
 from deepspeech.training.gradclip import MyClipGradByGlobalNorm
 
 from deepspeech.utils import mp_tools
-from deepspeech.utils.error_rate import char_errors
-from deepspeech.utils.error_rate import word_errors
-from deepspeech.utils.error_rate import cer
-from deepspeech.utils.error_rate import wer
-from deepspeech.utils.utility import print_grads
-from deepspeech.utils.utility import print_params
+from deepspeech.utils import layer_tools
+from deepspeech.utils import error_rate
 
 from deepspeech.io.collator import SpeechCollator
 from deepspeech.io.sampler import SortagradDistributedBatchSampler
@@ -59,7 +55,7 @@ class DeepSpeech2Trainer(Trainer):
         self.model.train()
         loss = self.model(*batch_data)
         loss.backward()
-        print_grads(self.model, logger=None)
+        layer_tools.print_grads(self.model, print_func=None)
         self.optimizer.step()
         self.optimizer.clear_grad()
 
@@ -127,7 +123,7 @@ class DeepSpeech2Trainer(Trainer):
         if self.parallel:
             model = paddle.DataParallel(model)
 
-        print_params(model, self.logger)
+        layer_tools.print_params(model, self.logger.info)
 
         grad_clip = MyClipGradByGlobalNorm(config.training.global_grad_clip)
         lr_scheduler = paddle.optimizer.lr.ExponentialDecay(
@@ -237,8 +233,8 @@ class DeepSpeech2Tester(DeepSpeech2Trainer):
     def compute_metrics(self, audio, texts, audio_len, texts_len):
         cfg = self.config.decoding
         errors_sum, len_refs, num_ins = 0.0, 0, 0
-        errors_func = char_errors if cfg.error_rate_type == 'cer' else word_errors
-        error_rate_func = cer if cfg.error_rate_type == 'cer' else wer
+        errors_func = error_rate.char_errors if cfg.error_rate_type == 'cer' else error_rate.word_errors
+        error_rate_func = error_rate.cer if cfg.error_rate_type == 'cer' else error_rate.wer
 
         vocab_list = self.test_loader.dataset.vocab_list
 
diff --git a/deepspeech/models/deepspeech2.py b/deepspeech/models/deepspeech2.py
index 374d15ef4..1173c852d 100644
--- a/deepspeech/models/deepspeech2.py
+++ b/deepspeech/models/deepspeech2.py
@@ -382,19 +382,45 @@ class DeepSpeech2Model(nn.Layer):
         """Build a model from a pretrained model.
         Parameters
         ----------
-        model: nn.Layer
-            Asr Model.
-        
         checkpoint_path: Path or str
             The path of pretrained model checkpoint, without extension name.
         
         Returns
         -------
-        Model
+        DeepSpeech2Model
             The model build from pretrined result.
         """
         checkpoint.load_parameters(self, checkpoint_path=checkpoint_path)
-        return
+        return self
+
+    @classmethod
+    def from_pretrained(cls, dataset, config, checkpoint_path):
+        """Build a DeepSpeech2Model model from a pretrained model.
+        Parameters
+        ----------
+        dataset: paddle.io.Dataset
+
+        config: yacs.config.CfgNode
+            model configs
+        
+        checkpoint_path: Path or str
+            the path of pretrained model checkpoint, without extension name
+        
+        Returns
+        -------
+        DeepSpeech2Model
+            The model built from pretrained result.
+        """
+        model = cls(feat_size=dataset.feature_size,
+                    dict_size=dataset.vocab_size,
+                    num_conv_layers=config.model.num_conv_layers,
+                    num_rnn_layers=config.model.num_rnn_layers,
+                    rnn_size=config.model.rnn_layer_size,
+                    use_gru=config.model.use_gru,
+                    share_rnn_weights=config.model.share_rnn_weights)
+        model.from_pretrained(checkpoint_path)
+        layer_tools.summary(model)
+        return model
 
 
 class DeepSpeech2InferModel(DeepSpeech2Model):
diff --git a/deepspeech/utils/layer_tools.py b/deepspeech/utils/layer_tools.py
new file mode 100644
index 000000000..46a354761
--- /dev/null
+++ b/deepspeech/utils/layer_tools.py
@@ -0,0 +1,78 @@
+# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import numpy as np
+from paddle import nn
+
+__all__ = [
+    "summary", "gradient_norm", "freeze", "unfreeze", "print_grads",
+    "print_params"
+]
+
+
+def summary(layer: nn.Layer, print_func=print):
+    num_params = num_elements = 0
+    print_func("layer summary:")
+    for name, param in layer.state_dict().items():
+        print_func("{}|{}|{}".format(name, param.shape, np.prod(param.shape)))
+        num_elements += np.prod(param.shape)
+        num_params += 1
+    print_func("layer has {} parameters, {} elements.".format(num_params,
+                                                              num_elements))
+
+
+def gradient_norm(layer: nn.Layer):
+    grad_norm_dict = {}
+    for name, param in layer.state_dict().items():
+        if param.trainable:
+            grad = param.gradient()
+            grad_norm_dict[name] = np.linalg.norm(grad) / grad.size
+    return grad_norm_dict
+
+
+def recursively_remove_weight_norm(layer: nn.Layer):
+    for layer in layer.sublayers():
+        try:
+            nn.utils.remove_weight_norm(layer)
+        except:
+            # ther is not weight norm hoom in this layer
+            pass
+
+
+def freeze(layer: nn.Layer):
+    for param in layer.parameters():
+        param.trainable = False
+
+
+def unfreeze(layer: nn.Layer):
+    for param in layer.parameters():
+        param.trainable = True
+
+
+def print_grads(model, print_func=print):
+    for n, p in model.named_parameters():
+        msg = f"param grad: {n}: shape: {p.shape} grad: {p.grad}"
+        if print_func:
+            print_func(msg)
+
+
+def print_params(model, print_func=print):
+    total = 0.0
+    for n, p in model.named_parameters():
+        msg = f"param: {n}: shape: {p.shape} stop_grad: {p.stop_gradient}"
+        total += np.prod(p.shape)
+        if print_func:
+            print_func(msg)
+    if print_func:
+        print_func(f"Total parameters: {total}!")
diff --git a/deepspeech/utils/utility.py b/deepspeech/utils/utility.py
index 7892f9150..72a45e29a 100644
--- a/deepspeech/utils/utility.py
+++ b/deepspeech/utils/utility.py
@@ -16,7 +16,7 @@
 import numpy as np
 import distutils.util
 
-__all__ = ['print_arguments', 'add_arguments', 'print_grads', 'print_params']
+__all__ = ['print_arguments', 'add_arguments']
 
 
 def print_arguments(args):
@@ -57,22 +57,4 @@ def add_arguments(argname, type, default, help, argparser, **kwargs):
         default=default,
         type=type,
         help=help + ' Default: %(default)s.',
-        **kwargs)
-
-
-def print_grads(model, logger=None):
-    for n, p in model.named_parameters():
-        msg = f"param grad: {n}: shape: {p.shape} grad: {p.grad}"
-        if logger:
-            logger.info(msg)
-
-
-def print_params(model, logger=None):
-    total = 0.0
-    for n, p in model.named_parameters():
-        msg = f"param: {n}: shape: {p.shape} stop_grad: {p.stop_gradient}"
-        total += np.prod(p.shape)
-        if logger:
-            logger.info(msg)
-    if logger:
-        logger.info(f"Total parameters: {total}!")
+        **kwargs)
\ No newline at end of file