add API document and fix some bugs

Signed-off-by: weichen <niweichen@chinamobile.com>
Change-Id: I6786189e98e43e0d0cb5936903ab773e35525348
diff --git a/docs/index.rst b/docs/index.rst
index f2b0185..cfaad6f 100644
--- a/docs/index.rst
+++ b/docs/index.rst
@@ -24,6 +24,7 @@
    license.rst
    release-notes.rst
    projects.rst
+   api-docs.rst
 
 
 Indices