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* added option for batching empty data, fixes #2526

* added option for batching empty data, fixes #2526

* decreased line lengths

* removed trailing whitespace

* fixed wrong feature name

* [Bugfix] stop erasing schema of frames w/ no cols (fixes #2528)

* removed arg doc
Co-authored-by: Quan (Andy) Gan <coin2028@hotmail.com>
Co-authored-by: Minjie Wang <wmjlyjemaine@gmail.com>