public ArrayNode expectArrayNode(String message) {
        throw new ExpectationNotMetException(expandMessage(message, NodeType.ARRAY.toString()), this);
    }
Casts the current node to an {@code ArrayNode}, throwing
{@link ExpectationNotMetException} when the node is the wrong type.

@param message Error message to use if the node is of the wrong type.
@return Returns an array node.
@throws ExpectationNotMetException when the node is the wrong type.
smithy-model/src/main/java/software/amazon/smithy/model/node/Node.java