Add a Python API to load model input examples

[maitre-matt]

What changes are proposed in this pull request?

This change adds a new Python API Model.load_input_example(), which wraps the internal-only method _read_example(). It allows tools which consume MLflow models to correctly load model input examples.

Associated Feature Request: #5211

How is this patch tested?

Added unit tests.

Does this PR change the documentation?

• No. You can skip the rest of this section.
• Yes. Make sure the changed pages / sections render correctly by following the steps below.

1. Check the status of the ci/circleci: build_doc check. If it's successful, proceed to the
   next step, otherwise fix it.
2. Click Details on the right to open the job page of CircleCI.
3. Click the Artifacts tab.
4. Click docs/build/html/index.html.
5. Find the changed pages / sections and make sure they render correctly.

Release Notes

Is this a user-facing change?

• No. You can skip the rest of this section.
• Yes. Give a description of this change to be included in the release notes for MLflow users.

Add a Python API to load model input examples

What component(s), interfaces, languages, and integrations does this PR affect?

Components

• area/artifacts: Artifact stores and artifact logging
• area/build: Build and test infrastructure for MLflow
• area/docs: MLflow documentation pages
• area/examples: Example code
• area/model-registry: Model Registry service, APIs, and the fluent client calls for Model Registry
• area/models: MLmodel format, model serialization/deserialization, flavors
• area/projects: MLproject format, project running backends
• area/scoring: MLflow Model server, model deployment tools, Spark UDFs
• area/server-infra: MLflow Tracking server backend
• area/tracking: Tracking Service, tracking client APIs, autologging

Interface

• area/uiux: Front-end, user experience, plotting, JavaScript, JavaScript dev server
• area/docker: Docker use across MLflow's components, such as MLflow Projects and MLflow Models
• area/sqlalchemy: Use of SQLAlchemy in the Tracking Service or Model Registry
• area/windows: Windows support

Language

• language/r: R APIs and clients
• language/java: Java APIs and clients
• language/new: Proposals for new client languages

Integrations

• integrations/azure: Azure and Azure ML integrations
• integrations/sagemaker: SageMaker integrations
• integrations/databricks: Databricks integrations

How should the PR be classified in the release notes? Choose one:

• rn/breaking-change - The PR will be mentioned in the "Breaking Changes" section
• rn/none - No description will be included. The PR will be mentioned only by the PR number in the "Small Bugfixes and Documentation Updates" section
• rn/feature - A new user-facing feature worth mentioning in the release notes
• rn/bug-fix - A user-facing bug fix worth mentioning in the release notes
• rn/documentation - A user-facing documentation change worth mentioning in the release notes

[ankit-db]

Thanks for filing the PR @maitre-matt - I'll add this to my review queue. It's a great idea!

[ankit-db]

Just a few brief comments

[ankit-db]

Thank you so much for the contribution! This one's going to be super useful for people 😄

[ankit-db]

@maitre-matt I think I may have messed up the signoff by accepting a suggestion which creates a commit. Will fix it tmm and merge!

[maitre-matt]

@maitre-matt I think I may have messed up the signoff by accepting a suggestion which creates a commit. Will fix it tmm and merge!

Thanks for the quick turnaround on that PR! Much appreciated. We are building ML tools and MLflow's standardization is making things a lot simpler.

[harupy]

Not a big issue, but we can remove the comma.

Suggested change

	from mlflow.models.utils import (
	_read_example,
	)
	from mlflow.models.utils import _read_example

[mmaitre314]

Reformatted to remove the comma