update docstrings

Author: yolagil

src/a2a/client/helpers.py

@@ -12,7 +12,17 @@ def create_text_message_object(
     extensions: list[Any] | None = None,
     metadata: dict[Any, Any] | None = None,
 ) -> Message:
-    """Create a Message object containing a single TextPart."""
+    """Create a Message object containing a single TextPart.
+
+    Args:
+        role: The role of the message sender (user or agent). Defaults to Role.user.
+        content: The text content of the message. Defaults to an empty string.
+        extensions: The extensions of the message. Defaults to an empty list.
+        metadata: The metadata of the message. Defaults to an empty dictionary.
+
+    Returns:
+        A `Message` object with a new UUID message_id.
+    """
     return Message(
         role=role,
         parts=[Part(TextPart(text=content or ''))],