from typing import List
from typing import Counter


def doc_freq(documents: List[List[str]]) -> dict:
    """
    Takes in a list of documents which each is a list of tokens and return a dictionary of frequencies for each token over all the documents. E.g. {"Aarhus": 20, "the": 2301, ...}
    """
    c = Counter()
    for l in documents:
        c.update(set(l))
    return dict(c)