Importing `AgentEvaluator` results in excluded dependency error

[d33bs]

Describe the bug
Thanks for the great work on this project! google-adk provides an evaluation framework which is useful for testing how agentic workflows process with flexibility beyond pass/fail metrics (as found in traditional software testing). I found that when prototyping with AgentEvaluator that there is a required dependency on tabulate which is excluded from the installation of google-adk. This could be resolved by adding tabulate as a dependency which is installed along with google-adk (thus preventing an error).

To Reproduce

Please see the following Google Colab notebook which demonstrates the behavior:
https://colab.research.google.com/drive/1tkV_XsPhQkecgJhDOjvxFMzLDNjvX07k

1. Install google-adk into Python environment
2. Attempt import: from google.adk.evaluation.agent_evaluator import AgentEvaluator
3. Witness error about missing tabulate dependency.

Expected behavior
I'd expect that after installing google-adk that I can successfully import and use AgentEvaluator without additional imports (unless needed for customization within external projects).

Screenshots

Desktop (please complete the following information):

• OS: MacOS, Linux
• Python version(python -V): 3.11
• ADK version(pip show google-adk): 1.2.1

Additional context
n/a

[hangfei]

we have a eval extra dependency needs to be installed(https://github.com/google/adk-python/blob/main/pyproject.toml#L74).

We didn't documented properly or maybe we can provide some warnings if people use eval but didn't install the dependency properly. @ankursharmas

[d33bs]

Thanks @hangfei ! I did miss the extra within the pyprojec.toml, my apologies for missing this the first go around. As you suggested, extra documentation might be nice near where the pip installation is first mentioned within the docsite (perhaps this could appear just after the primary pip install).