fter
 this method is called, the caller can safely assume no value was set.
 </p>

 <p>
 If this resolver was constructed in read-only mode, this method will always throw
 <code>PropertyNotWritableException</code>.
 </p>

 <p>
 If a <code>Map</code> was created using <a href="https://docs.oracle.com/javase/7/docs/api/java/util/Collections.html?is-external=true#unmodifiableMap-java.util.Map-" title="class or interface in java.util"><code>Collections.unmodifiableMap(java.util.Map&lt;? extends K, ? extends V&g