def METHOD_NAME(self, class_imbalance_ratio_th: float = 0.1):
    """Add condition - ratio between least to most frequent labels.
    This ratio is compared to class_imbalance_ratio_th.
    Parameters
    ----------
    class_imbalance_ratio_th: float, default: 0.1
        threshold for least frequent label to most frequent label.
    """
    name = 'The ratio between least frequent label to most frequent label ' \
           f'is less than or equal {class_imbalance_ratio_th}'
    def threshold_condition(result: t.Dict[Hashable, float]) -> ConditionResult:
        class_ratio = result[list(result.keys())[-1]] / result[list(result.keys())[0]]
        details = f'The ratio between least to most frequent label is {format_number(class_ratio)}'
        if class_ratio >= class_imbalance_ratio_th:
            return ConditionResult(ConditionCategory.WARN, details)
        return ConditionResult(ConditionCategory.PASS, details)
    return self.add_condition(name, threshold_condition)