A content block whose type is not one this SDK models — a future or
vendor-specific kind. The entire inbound block (including its original
type) is stored verbatim so it round-trips losslessly through
toJson/fromJson instead of being silently coerced into empty text.
A content block whose type is not one this SDK models — a future or vendor-specific kind. The entire inbound block (including its original type) is stored verbatim so it round-trips losslessly through toJson/fromJson instead of being silently coerced into empty text.