public String getHeader(String name) {
        List<String> values = parent.headers().get(name);
        if (values == null || values.isEmpty()) {
            return null;
        }
        return values.get(values.size() - 1);
    }
Sets a header with the given name and value.
If the header had already been set, the new value overwrites the previous one.
container-core/src/main/java/com/yahoo/jdisc/http/filter/DiscFilterRequest.java