/**
  * Method for locating all back-reference properties (setters, fields) bean has
  *
  * @since 1.6
  */
 public Map<String, AnnotatedMember> findBackReferenceProperties() {
   HashMap<String, AnnotatedMember> result = null;
   for (BeanPropertyDefinition property : _properties) {
     AnnotatedMember am = property.getMutator();
     if (am == null) {
       continue;
     }
     AnnotationIntrospector.ReferenceProperty refDef =
         _annotationIntrospector.findReferenceType(am);
     if (refDef != null && refDef.isBackReference()) {
       if (result == null) {
         result = new HashMap<String, AnnotatedMember>();
       }
       String refName = refDef.getName();
       if (result.put(refName, am) != null) {
         throw new IllegalArgumentException(
             "Multiple back-reference properties with name '" + refName + "'");
       }
     }
   }
   return result;
 }