Add to_ordinal feature for ordinal regression/classification

[awsaf49]

This PR adds the feature to_ordinal for ordinal regression/classification mentioned in issue keras-team/tf-keras#321

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[awsaf49]

@gbaned please approve the workflows.

[hertschuh]

Thank you for the Pull Request!
Just a small change:

[haifeng-jin]

Thanks for the PR!
Please also update this file after the PR is merged, by adding to the tf.keras section for new features.

[haifeng-jin]

@awsaf49 Seems the self.assertTrue() in the test is failing. Would you please fix it? Thanks.

[haifeng-jin]

LGTM

[haifeng-jin]

@awsaf49
The tests are still failing.

ERROR: test_to_ordinal (__main__.TestNPUtils)
TestNPUtils.test_to_ordinal
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/kbuilder/.cache/bazel/_bazel_kbuilder/31d6f47147b75c35404d734345be7323/execroot/org_keras/bazel-out/k8-opt/bin/keras/utils/np_utils_test.runfiles/org_keras/keras/utils/np_utils_test.py", line 74, in test_to_ordinal
    self.assertTrue(
  File "/usr/lib/python3.9/unittest/case.py", line 686, in assertTrue
    if not expr:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

----------------------------------------------------------------------
Ran 3 tests in 0.006s

[awsaf49]

@awsaf49 The tests are still failing.

ERROR: test_to_ordinal (__main__.TestNPUtils)
TestNPUtils.test_to_ordinal
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/kbuilder/.cache/bazel/_bazel_kbuilder/31d6f47147b75c35404d734345be7323/execroot/org_keras/bazel-out/k8-opt/bin/keras/utils/np_utils_test.runfiles/org_keras/keras/utils/np_utils_test.py", line 74, in test_to_ordinal
    self.assertTrue(
  File "/usr/lib/python3.9/unittest/case.py", line 686, in assertTrue
    if not expr:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

----------------------------------------------------------------------
Ran 3 tests in 0.006s

@haifeng-jin my bad, forgot to put np.all after element-wise comaprision, will fix it in the following commit

[awsaf49]

This PR is stuck due to

1 workflow awaiting approval, First-time contributors need a maintainer to approve running workflows.

@gbaned could you please approve?

[awsaf49]

I think this PR looks fine but is on hold for quite some time, It would be really helpful if someone could merge the PR.
cc: @haifeng-jin @hertschuh @gbaned

[haifeng-jin]

@awsaf49 I am doing some required Google internal changes since this PR touches the APIs. Sorry for the delay.

[awsaf49]

@haifeng-jin thanks for your effort. I wasn't aware of these internal procedures. Looking forward to hearing from you...

[haifeng-jin]

@awsaf49 There are more internal review comments that I need to address. So please expect some delays. Thanks.

[awsaf49]

@awsaf49 There are more internal review comments that I need to address. So please expect some delays. Thanks.

@haifeng-jin Thank you for letting me know.

In the meantime, I would like to propose creating an example on Ordinal Regression, something like "Age Estimation with Ordinal Regression" on the keras.io/examples page. As of now, there is no mention of Ordinal Regression on the call for contribution page. May I proceed with creating a pull request for this example?

cc: @fchollet

[awsaf49]

@haifeng-jin as the PR has been merged, I've created a PR on TensorFlow to update the RELEASE.md file as you asked, tensorflow/tensorflow/pull/59436