public ObjectNode expectStringMember(String key, Consumer<String> consumer) {
        consumer.accept(expectStringMember(key).getValue());
        return this;
    }
Requires that {@code key} exists, is a string, and passes the value to {@code consumer}.

@param key Key to retrieve.
@param consumer Consumer that accepts the string value.
@return Returns the node.
smithy-model/src/main/java/software/amazon/smithy/model/node/ObjectNode.java