def lang_freq(self, lang):
        
        if lang not in self._all_lang_freq:
            self._all_lang_freq[lang] = self._load_lang_ngrams(lang)

        return self._all_lang_freq[lang]
Adds a single HTTP header to the headers to be sent on the request.
dataset/ETHPy150Open nltk/nltk/nltk/corpus/reader/crubadan.py/CrubadanCorpusReader.lang_freq--crossover with--dataset/ETHPy150Open Lukasa/hyper/hyper/http20/stream.py/Stream.add_header