youkaichao 2564e989fb Improve Batch (#126)
* make sure the key type of Batch is string, and add unit tests

* add is_empty() function and unit tests

* enable cat of mixing dict and Batch, just like stack
2020-07-13 17:33:01 +08:00
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2020-06-03 13:59:47 +08:00
2020-07-13 17:33:01 +08:00