Jiaming Yuan 6c9b6f11da Use cudf.concat explicitly. (#4918)
* Use `cudf.concat` explicitly.

* Add test.
2019-10-10 16:02:10 +13:00
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2019-09-16 23:52:00 -04:00
2018-11-15 13:56:33 +13:00
2019-08-19 16:51:40 +12:00