public <T> ObjectNode expectMember(String key, Function<Node, T> mapper, Consumer<T> consumer) {
        consumer.accept(mapper.apply(expectMember(key)));
        return this;
    }
Requires that the {@code key} member is present, passes the value through the given {@code mapper}, and then
passes the mapped value to {@code consumer}.

@param key Key to get from the object.
@param mapper Mapping function used to convert the node value.
@param consumer Consumer to pass the found value to.
@param <T> Mapped value type.
@return Returns the node.
smithy-model/src/main/java/software/amazon/smithy/model/node/ObjectNode.java