docs: private Set<Object> scan() {
          Set<Object> mocks = newMockSafeHashSet();
          for (Field field : clazz.getDeclaredFields()) {
              // mock or spies only
              FieldReader fieldReader = new FieldReader(instance, field);
  
              Object mockInstance = preparedMock(fieldReader.read(), field);
              if (mockInstance != null) {
                  mocks.add(mockInstance);
              }
          }
          return mocks;
      }