public static <C> List<C> fetch(Class<C> cls, DatabaseObject filteredBy) {
    Database database = filteredBy.getDatabase();

    @SuppressWarnings("unchecked")
    AnnotatedRecordMapper<DatabaseObject> parentMapper =
        (AnnotatedRecordMapper<DatabaseObject>) create(filteredBy.getClass());
    AnnotatedRecordMapper<?> mapper = create(cls);

    List<String> relationColumnNames = mapper.getRelationColumnNames(filteredBy.getClass());
    List<String> idColumnNames = parentMapper.getIdColumnNames();
    Map<String, Object> values = parentMapper.extractIds(filteredBy);

    String relationExpression = "";
    Object[] parameters = new Object[relationColumnNames.size()];

    for (int i = 0; i < relationColumnNames.size(); i++) {
      relationExpression += relationColumnNames.get(i) + "=?";
      parameters[i] = values.get(idColumnNames.get(i));

      if (parameters[i] == null) {
        return new ArrayList<>();
      }
    }

    try (Transaction transaction = database.beginReadOnlyTransaction()) {
      transaction.associate(filteredBy);

      return transaction.select(cls, relationExpression, parameters);
    }
  }
    public void toStorageType(Object value, Map<String, Object> valuesRef) {
      Object[] values = null;

      if (isRelation(getType())) {
        if (value != null) {
          @SuppressWarnings("unchecked")
          AnnotatedRecordMapper<Object> mapper = (AnnotatedRecordMapper<Object>) create(getType());

          values = mapper.getIds(value);
        }
      } else if (isEmbedded()) {
        if (value != null) {
          values = getEmbeddedFields(value);
        }
      } else {
        values = new Object[] {dataTypeConverter.toStorageType(value)};
      }

      if (values != null) {
        for (int i = 0; i < names.length; i++) {
          valuesRef.put(names[i], values[i]);
        }
      } else {
        for (String columnName : names) {
          valuesRef.put(columnName, null);
        }
      }
    }
  @SuppressWarnings("unchecked")
  public static <T extends DatabaseObject> T fetch(T instance) {
    Database database = instance.getDatabase();
    Object[] ids;

    synchronized (STUBS) {
      ids = STUBS.get(instance);
    }

    if (database == null || ids == null) {
      return instance;
    }

    AnnotatedRecordMapper<? extends Object> mapper = create(instance.getClass());

    String whereClause = "";

    for (String fieldName : mapper.getIdColumnNames()) {
      if (!whereClause.isEmpty()) {
        whereClause += " AND ";
      }
      whereClause += fieldName + "=?";
    }

    try (Transaction transaction = database.beginReadOnlyTransaction()) {
      return (T) transaction.selectUnique(instance.getClass(), whereClause, ids);
    }
  }