 were not met. In the event that preconditions were not met, the returned
 <code>ResponseBuilder</code> instance will have an appropriate status and will also include a <code>Vary</code> header if the
 <a href="#selectVariant(java.util.List)"><code>selectVariant(List)</code></a> method was called prior to to calling <code>evaluatePreconditions</code>. It is the
 responsibility of the caller to check the status and add additional metadata if required. E.g., see
 <a href="http://www.w3.org/Protocols/rfc2616/r