Implement isreal function in keras.ops

[shashaka]

Adds keras.ops.isreal, which tests element-wise whether each tensor element has zero imaginary part.
Supported across NumPy, TensorFlow, PyTorch, and JAX backends.
Not supported on OpenVINO.

[gemini-code-assist]

Summary of Changes

Hello @shashaka, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces the isreal function to the Keras operations API, providing a consistent and backend-agnostic way to determine if tensor elements are real numbers. This enhancement improves Keras's numerical capabilities, particularly when dealing with complex numbers. Additionally, an implementation for a poly function was included in the TensorFlow backend, which seems to be an unrelated feature.

Highlights

• New isreal function: A new keras.ops.isreal function has been introduced, designed to test element-wise whether each tensor element has a zero imaginary part, effectively checking if it's a real number.
• Multi-backend support: The isreal function is implemented and supported across multiple Keras backends, including NumPy, TensorFlow, PyTorch, and JAX, ensuring consistent behavior regardless of the chosen backend.
• API exposure and testing: The new function is properly exposed through the keras.ops and keras.ops.numpy public APIs. Comprehensive unit tests have been added to verify its functionality, symbolic shape inference, and dtype consistency across various backends and data types.
• Unrelated poly function addition: An implementation for a poly function was also added to the TensorFlow backend, which appears to be an independent change not directly related to the isreal function.

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[gemini-code-assist]

Code Review

This pull request correctly implements the isreal operation across the JAX, NumPy, PyTorch, and TensorFlow backends, along with the necessary exports and tests. However, there are a few issues to address. An unrelated poly function has been added to the TensorFlow backend, which should be removed. Additionally, a test for isposinf was mistakenly replaced by a test for isreal instead of adding a new one. Lastly, the docstring for the isreal function is missing a code example, which is required by the repository's style guide.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.10345% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.63%. Comparing base (3137cb0) to head (0e5ce37).
⚠️ Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
keras/api/_tf_keras/keras/ops/__init__.py	0.00%	1 Missing ⚠️
keras/api/_tf_keras/keras/ops/numpy/__init__.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21740      +/-   ##
==========================================
+ Coverage   82.59%   82.63%   +0.04%     
==========================================
  Files         572      572              
  Lines       58535    58533       -2     
  Branches     9158     9146      -12     
==========================================
+ Hits        48345    48368      +23     
+ Misses       7853     7840      -13     
+ Partials     2337     2325      -12     

Flag	Coverage Δ
keras	82.43% <93.10%> (+0.04%)	⬆️
keras-jax	63.21% <62.06%> (+0.01%)	⬆️
keras-numpy	57.57% <62.06%> (+0.01%)	⬆️
keras-openvino	34.36% <34.48%> (+0.03%)	⬆️
keras-tensorflow	63.96% <68.96%> (+0.02%)	⬆️
keras-torch	63.50% <62.06%> (+0.01%)	⬆️

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[hertschuh]

Thanks for the PR!