Performance issues in tf_coder/datasets/github/data_loader.py(P2)

[DLPerf]

Hello,I found a performance issue in the definition of load_data ,
tf_coder/datasets/github/data_loader.py,
dataset = dataset.map(parse_example_proto) was called without num_parallel_calls.
I think it will increase the efficiency of your program if you add this.

Here is the documemtation of tensorflow to support this thing.

Looking forward to your reply. Btw, I am very glad to create a PR to fix it if you are too busy.

[kensens]

Thank you for your comment, but the affected code is not used often, so this is low priority for us.