Fix dygraph lac (#4203)

* lac dygraph for version 1.7

* lac dygraph for version 1.7

* add eval, predict and README

* remove unused links

* fix lac_dygraph download and README

dygraph/lac/README.md

@@ -23,7 +23,7 @@ Lexical Analysis of Chinese，简称 LAC，是一个联合的词法分析模型
 克隆工具集代码库到本地
 ```bash
  git clone https://github.com/PaddlePaddle/models.git
- cd models/PaddleNLP/lexical_analysis
+ cd https://github.com/PaddlePaddle/models/tree/develop/dygraph/lac
 ```
 
 #### 3. 环境依赖

dygraph/lac/downloads.py

@@ -28,6 +28,7 @@ import tarfile
 import requests
 
 FILE_INFO = {
+    'BASE_URL': 'https://baidu-nlp.bj.bcebos.com/',
     'DATA': {
         'name': 'lexical_analysis-dataset-2.0.0.tar.gz',
         'md5': '71e4a9a36d0f0177929a1bccedca7dba'
@@ -38,7 +39,7 @@ FILE_INFO = {
 def usage():
     desc = ("\nDownload datasets and pretrained models for LAC.\n"
             "Usage:\n"
-            "   1. python download.py dataset\n"
+            "   1. python download.py dataset\n")
     print(desc)