[DRAFT] trulens-legacy and trulens-api

[sfc-gh-pmardziel]

This PR is being split into multiple ones. Keep this open until the splits are merged:

• Trulens legacy part here: trulens-legacy #1345

Description

Creates trulens-legacy package:

1. Preserved trulens_eval.* names defined in __init__.py files for backwards compatibility to be deprecated later. Until then, a warning is issued of an old module is imported or a class or function imported via the old name is invoked. This is tested by new "static" tests in test_deprecation.py.

Example warning when importing from trulens_eval

from trulens_eval import Tru

DeprecationWarning: The `trulens_eval` module is deprecated. See https://trulens.org/docs/migration-guide for instructions on migrating to `trulens.*` modules.

Example warning when using something imported from trulens_eval:

Tru(...)

DeprecationWarning: Class `Tru` has moved:
    New import: `from trulens.core.tru import Tru`
 See https://trulens.org/docs/migration-guide for instructions on migrating to `trulens` modules.

3. Brought back some utilities for optional imports which will not be needed after the package is removed in the future. Optional imports are used to preserve how trulens_eval behaved with respect to optional imports in the past. However, in many cases, the packages that need to be installed have been changed to the optional trulens-* packages instead of what was is now these packages' dependencies.

4. Added versioning and deprecation policies doc POLICIES.md and included it in the contributing nav item group.

5. (TODO, waiting for another PR for testing this). Preserve other trulens_eval names that are public enough that they need to have aliases for some time before removal.

6. Created trulens-api package containing the Interactive API. This provides the trulens.api module and submodules for a public, package-independent, access to trulens components like Tru:

from trulens.api import Tru

Some lookups are dynamic into the various trulens-* packages and either install the packages automatically or give the user instructions on installing additional packages if appropriate. The installation is the default but can be disabled. For example:

from trulens.api.providers import Cortex

If trulens-providers-cortex is installed, the above will work. If it is not installed, an instruction is issued alongside the import error:

RuntimeError: Package trulens-providers-cortex is not installed. Enable automatic installation by calling `trulens.api.set_no_install(False)` or install it manually with pip: 
    ```bash
    pip install 'trulens-providers-cortex'
    ```

The interactive API also gives better import errors if someone tries to import something that does not exist showing information of what is actually contained in the api modules and whether the optional packages that they need are installed:

from trulens.api import Blah

Output:

...
ImportError: Module trulens.api has no attribute Blah.
Module 'trulens.api' from '/Users/pmardziel/repos/truera/trulens/src/api/trulens/api/__init__.py contains:
provider: 
  Bedrock	[trulens-providers-bedrock]	[1.0.1a0]
  Cortex	[trulens-providers-cortex]	[not installed]
  Huggingface	[trulens-providers-huggingface]	[1.0.1a0]
  HuggingfaceLocal	[trulens-providers-huggingface]	[1.0.1a0]
  Langchain	[trulens-providers-langchain]	[1.0.1a0]
  LiteLLM	[trulens-providers-litellm]	[1.0.1a0]
  OpenAI	[trulens-providers-openai]	[1.0.1a0]
  AzureOpenAI	[trulens-providers-openai]	[1.0.1a0]
recorder: 
  TruBasicApp	[trulens-core]	[1.0.1a0]
  TruCustomApp	[trulens-core]	[1.0.1a0]
  TruVirtual	[trulens-core]	[1.0.1a0]
  TruChain	[trulens-instrument-langchain]	[1.0.1a0]
  TruLlama	[trulens-instrument-llamaindex]	[1.0.1a0]
  TruRails	[trulens-instrument-nemo]	[not installed]
class: 
  Tru	[trulens-core]	[1.0.1a0]
  TP	[trulens-core]	[1.0.1a0]
  Feedback	[trulens-core]	[1.0.1a0]
  Provider	[trulens-core]	[1.0.1a0]
enum: 
  FeedbackMode	[trulens-core]	[1.0.1a0]
  FeedbackResultStatus	[trulens-core]	[1.0.1a0]
  FeedbackOnMissingParameters	[trulens-core]	[1.0.1a0]
  FeedbackCombinations	[trulens-core]	[1.0.1a0]
utility: 
  Select	[trulens-core]	[1.0.1a0]
  set_no_install	[trulens-api]	[1.0.1a0]
schema: 
  FeedbackResult	[trulens-core]	[1.0.1a0]
  FeedbackCall	[trulens-core]	[1.0.1a0]
  FeedbackDefinition	[trulens-core]	[1.0.1a0]

Importing from this module will install the required package. You can disable this by calling `trulens.api.set_no_install()`.

7. Added a main API reference index page that describes the Interactive API and the behaviour summarized here.

Other details good to know for developers

Please include any other details of this change useful for TruLens developers.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to
  not work as expected)
• This change requires a documentation update

[sfc-gh-pdharmana]

@sfc-gh-pmardziel can you please remove all the format changes in this PR and just include backwards compat. Also change the title of the PR?

[sfc-gh-dkurokawa]

I didn't check:

1. The poetry.lock files as these are auto-generated.
2. Can you spin the trulens.api stuff into a separate PR that's not as urgent.
3. In the future when you do a mass renaming can you put it in its own PR. That way the reviewers don't have to look at it as it's just a simple find and replace.