allow input null for text docs input

[ylwu-amzn]

Description

We need to support null value for some use case, for example multi-modal model needs text and image input. User who use TextDocsInputDataSet can use such format [text, image], the first item is text and second is image, but they could be null, for example user may only input image, the input will be [null, image]

Issues Resolved

[List any issues this PR will resolve]

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[dhrubo-os]

What happens if the input is [null, null]?

[ylwu-amzn]

This depends on the model. If model can't accept, it will throw exception.

[codecov]

Codecov Report

Merging #1401 (bc86c39) into main (358354c) will decrease coverage by 1.26%.
Report is 6 commits behind head on main.
The diff coverage is 57.98%.

@@             Coverage Diff              @@
##               main    #1401      +/-   ##
============================================
- Coverage     78.82%   77.56%   -1.26%     
- Complexity     2145     2178      +33     
============================================
  Files           168      173       +5     
  Lines          8755     8977     +222     
  Branches        878      889      +11     
============================================
+ Hits           6901     6963      +62     
- Misses         1455     1611     +156     
- Partials        399      403       +4     

Flag	Coverage Δ
ml-commons	77.56% <57.98%> (-1.26%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...rg/opensearch/ml/client/MachineLearningClient.java	100.00% <100.00%> (ø)
...earch/ml/engine/algorithms/TextEmbeddingModel.java	100.00% <100.00%> (ø)
...thms/sparse_encoding/SparseEncodingTranslator.java	100.00% <100.00%> (ø)
...rse_encoding/TextEmbeddingSparseEncodingModel.java	100.00% <100.00%> (ø)
...ing/HuggingfaceTextEmbeddingServingTranslator.java	100.00% <ø> (ø)
...NNXSentenceTransformerTextEmbeddingTranslator.java	67.04% <ø> (ø)
...ng/SentenceTransformerTextEmbeddingTranslator.java	100.00% <100.00%> (+2.38%)	⬆️
...rithms/text_embedding/TextEmbeddingDenseModel.java	91.30% <100.00%> (ø)
...va/org/opensearch/ml/engine/utils/ScriptUtils.java	90.00% <100.00%> (+13.52%)	⬆️
...tion/prediction/TransportPredictionTaskAction.java	78.26% <100.00%> (+0.48%)	⬆️
... and 10 more

... and 2 files with indirect coverage changes

[opensearch-trigger-bot]

The backport to 2.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.x 2.x
# Navigate to the new working tree
cd .worktrees/backport-2.x
# Create a new branch
git switch --create backport/backport-1401-to-2.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 f1dd56bb46554c6c0469c5c0222cf618ef1031b3
# Push it to GitHub
git push --set-upstream origin backport/backport-1401-to-2.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.x

Then, create a pull request where the base branch is 2.x and the compare/head branch is backport/backport-1401-to-2.x.