def METHOD_NAME(
    self, dataset_name: str, feature_name: str, global_mean: float, global_count: float
) -> float:
    df = self.data[dataset_name]
    tmp = (df[feature_name] - global_mean) * (df[feature_name] - global_mean)
    variance = tmp.sum() / (global_count - 1)
    return variance.item()