from typing import List
from typing import Tuple


def clean_truths(
    truths: List[str], predictions: List[str]
) -> Tuple[List[str], List[str]]:
    """
    Remove classes that the classifier doesn't know.

    Parameters
    ----------
    truths : List[int]
    predictions : List[int]

    Returns
    -------
    truths, predictions : List[int], List[int]
    """
    preds = []
    truths_tmp = []
    for tru, pred in zip(truths, predictions):
        if tru in predictions:
            truths_tmp.append(tru)
            preds.append(pred)
    predictions = preds
    truths = truths_tmp
    return truths, predictions