code: public final void remove(final String key) {
          final Property prop = find(key);
          if (prop != null) {
              prop.setValue(null);
          }
      }
docs: Remove the property with the given key. The internal property object is not deleted itself but it's value is set to <code>null</code>
  and the method <code>isDeleted()</code> will return <code>true</code> .
  
  @param key
  Key for the property to remove.