Design of class genai.Content

While developing Agent's with Google's ADK, I discovered them using `genai.Content` and I saw they use this condition:

`if event.content and event.content.parts:` : The full code is available [here](https://google.github.io/adk-docs/tutorials/agent-team/#step-1-your-first-agent-basic-weather-lookup) (Do Ctrl + F and type in the the if condition).

Now, the class Content is as follows:
```python
class Content(_common.BaseModel):
"""Contains the multi-part content of a message."""

parts: Optional[list[Part]] = Field(
default=None,
description="""List of parts that constitute a single message. Each part may have
a different IANA MIME type.""",
)
role: Optional[str] = Field(
default=None,
description="""Optional. The producer of the content. Must be either 'user' or
'model'. Useful to set for multi-turn conversations, otherwise can be
empty. If role is not specified, SDK will determine the role.""",
)
````

There is not a separate validation, but it is safe to assume that there will not be any response which has a role, but no parts.

Now even if you do encounter a possibility where out of user or model (as role field) , only role is set, then is not it a vague design from the genai repo? I mean there is a role but empty list as output.

When I asked them this [question](https://github.com/google/adk-python/issues/1543#issuecomment-3006939872), they said that I should ask you guys.

Feel free to counter me by all means.