code: public static Field[] filterDeepFields(Class clazz) {
          Field[] fields = Utils.getAllFields(clazz);
          List<Field> filtered = new ArrayList<>();
          for (Field f : fields) {
              if (f.isAnnotationPresent(DeepField.class)) {
                  filtered.add(f);
              }
          }
          return filtered.toArray(new Field[filtered.size()]);
      }
docs: Utility method that filters out all the fields _not_ annotated
  with the {@link com.stratio.deep.commons.annotations.DeepField} annotation.
  
  @param clazz the Class object for which we want to resolve deep fields.
  @return an array of deep Field(s).