SeqBlobReader Implementation (#29888)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/29888
Extract some common functions out of class LoadOp.
Reviewed By: yinghai, ipiszy
Differential Revision: D18456785
fbshipit-source-id: d0b8e86ad5709c35f1dc3821376000db1114dc95
