public ObjectNode expectObjectNode(Supplier<String> message) {
        return expectObjectNode(message.get());
    }
Casts the current node to an {@code ObjectNode}, throwing
{@link ExpectationNotMetException} when the node is the wrong type.

@param message Error message supplier.
@return Returns an object node.
@throws ExpectationNotMetException when the node is not an {@code ObjectNode}.
smithy-model/src/main/java/software/amazon/smithy/model/node/Node.java