private void refreshPropertyDescriptors() {
        PropertyUtils.clearDescriptors();
        pd = null;
        propertyDescriptorsRefreshed = true;
    }
Cleans out the {@link PropertyDescriptor} cache; when suspecting that
our PropertyDescriptor has lost its references, we want it to be re-built
(instead of getting the same instance from the cache).
core/src/main/java/com/github/dozermapper/core/propertydescriptor/JavaBeanPropertyDescriptor.java