Julia Shenshina

We already do 🤔 How to check ``` from etna.datasets import generate_ar_df, TSDataset df = generate_ar_df(periods=100, start_time="2020-01-01", n_segments=2) df = df[~((df.segment == "segment_0") & (df.timestamp.between("2020-01-10", "2020-01-30")))] df = TSDataset.to_dataset(df) ts...

Possible hotfix: create dummy metric that does not check timestamps for `y_true` and `y_pred` and change `MAE` metric with it [here](https://github.com/tinkoff-ai/etna/blob/8a8cefa5fb56337309aae78379ec3fa35595f942/etna/pipeline/base.py#L227). It can cause some problems [here](https://github.com/tinkoff-ai/etna/blob/8a8cefa5fb56337309aae78379ec3fa35595f942/etna/pipeline/base.py#L230-L231), so we need...