_l2_relative_errorm

Hello, I would like to ask how much of a range is considered valid for "_l2_relative_error "(modulus/sym/domain/validator/validator.py) ?
Over what range is “_l2_relative_error” considered valid Especially in fluid dynamics?

@staticmethod
def _l2_relative_error(true_var, pred_var):  # TODO replace with metric classes
    new_var = {}
    for key in true_var.keys():
        new_var["l2_relative_error_" + str(key)] = torch.sqrt(
            torch.mean(torch.square(true_var[key] - pred_var[key]))
            / torch.var(true_var[key])
        )
    return new_var

Thank you!