[Relay][Frontend] Implement SpaceToBatchND in Tensorflow frontend

[alexeyr]

Adds a missing auxiliary operation used for dilated pooling and convolutions.

[alexeyr]

@srkreddy1238 Please review

[srkreddy1238]

Thanks @alexeyr for adding this op.

Can you add few test cases to non zero values for padding ?

You may add the test cases directly from https://www.tensorflow.org/api_docs/cc/class/tensorflow/ops/space-to-batch-n-d too.

[alexeyr]

@srkreddy1238 I've added the tests based on these examples and TF tests. I believe there is a typo in one of the TF examples: tensorflow/tensorflow#27638.

[alexeyr]

@srkreddy1238 Actually, now that I know BatchToSpaceND exists, might as well add it too. I'll try to do it today.

[alexeyr]

@srkreddy1238 Would you object to:

1. Automatically detecting all test_ functions in the __main__ section so we can't forget to add them (as I did here initially);
2. Modifying compare_tf_to_tvm signature so you don't need to handle names explicitly?

[srkreddy1238]

1. Automatically detecting all test_ functions in the __main__ section so we can't forget to add them (as I did here initially);

The main is only for local execution as CI runs with nose. Any welcome to make this change.

2. Modifying compare_tf_to_tvm signature so you don't need to handle names explicitly?

Name handling is good as it's important to make sure that Input and output names being untouched from original Tensorflow graph. Advice to leave it as it is for now.

[srkreddy1238]

Can you compute the desired from TF API instead ?

[alexeyr]

Yes, I've made this change already, just not pushed yet.

[alexeyr]

The main is only for local execution as CI runs with nose. Any welcome to make this change.

Ah, ok, then I don't need to worry about it. Still will probably do it just to make clear.

Name handling is good as it's important to make sure that Input and output names being untouched from original Tensorflow graph. Advice to leave it as it is for now.

I think this could be handled entirely within the test and not exposed. But will leave for now, as you suggest.

[alexeyr]

@srkreddy1238 Added BatchToSpaceND.

[srkreddy1238]

LGTM