chore: GenAI Client(evals) - change event_time type to string in evals.Event

PiperOrigin-RevId: 878598319

Author: jsondai

vertexai/_genai/types/evals.py

@@ -267,8 +267,9 @@ class AgentEvent(_common.BaseModel):
     content: Optional[genai_types.Content] = Field(
         default=None, description="""The content of the event."""
     )
-    event_time: Optional[datetime.datetime] = Field(
-        default=None, description="""The timestamp when the event occurred."""
+    event_time: Optional[str] = Field(
+        default=None,
+        description="""The timestamp when the event occurred in RFC3339 format (e.g. '2026-03-03T00:42:32Z').""",
     )
     state_delta: Optional[dict[str, Any]] = Field(
         default=None,
@@ -292,8 +293,8 @@ class AgentEventDict(TypedDict, total=False):
     content: Optional[genai_types.ContentDict]
     """The content of the event."""
 
-    event_time: Optional[datetime.datetime]
-    """The timestamp when the event occurred."""
+    event_time: Optional[str]
+    """The timestamp when the event occurred in RFC3339 format (e.g. '2026-03-03T00:42:32Z')."""
 
     state_delta: Optional[dict[str, Any]]
     """The change in the session state caused by this event.