add license and reference for some models, test=doc

paddlespeech/t2s/models/hifigan/hifigan.py

@@ -1,7 +1,17 @@
-# -*- coding: utf-8 -*-
-"""HiFi-GAN Modules.
-This code is based on https://github.com/jik876/hifi-gan.
-"""
+# Copyright (c) 2022 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.
+# This code is based on https://github.com/jik876/hifi-gan.
 import copy
 from typing import Any
 from typing import Dict

paddlespeech/t2s/models/tacotron2/tacotron2.py

@@ -11,6 +11,7 @@
 # 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.
+# Modified from espnet(https://github.com/espnet/espnet)
 """Tacotron 2 related modules for paddle"""
 import logging
 from typing import Dict

paddlespeech/t2s/models/wavernn/wavernn.py

@@ -11,6 +11,7 @@
 # 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.
+# Modified from https://github.com/fatchord/WaveRNN
 import sys
 import time
 from typing import List