TS-2174: Assign proper type for uninitialized expression token

In librecords, not all token are register at initialization,
we must assign proper type if it is undefined.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>
TS-2177: Add invoke utility method to APIHooks.
TS-858 Updated the docs to 128MB examples

This avoids the confusion of examples being smaller than
the minimum disk cache size we have.