Fix Bug: stop filtering events that contain function responses

[alimosaed]

What is the problem?
As part of the preparation for an LLM call, the ADK will look through the session’s event list to create the LLM message history. As part of this, it filters out all events that don’t have any content or roles. Additionally, it will filter out any events that don’t have any text. Unfortunately, there are cases where there are events that just contain the function_response. These events are filtered mistakenly as well.

How did we fix this problem?
We've updated the event filtering condition to cover events that contain function_response.

How to reproduce this problem?
A sample script has been attached. It creates a user, llm and tool event. The tool is a simple function call that returns only the function_response. This event is filtered via ADK.

Reproduce the bug

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[ankursharmas]

This is an intentional choice to filter out function calls and responses of previous events. But this doesn't mean that the function responses were never provided to the model. For a function call triggered by the model, the response was provided to it, only for previous events these get hidden.