':type src_phrase: tuple(str)
:type trg_phrase: tuple(str)
:param log_prob: Log probability that given ``src_phrase``,
``trg_phrase`` is its translation
:type log_prob: float'

def add(self, src_phrase, trg_phrase, log_prob):

    entry = PhraseTableEntry(trg_phrase=trg_phrase, log_prob=log_prob)
    if (src_phrase not in self.src_phrases):
        self.src_phrases[src_phrase] = []
    self.src_phrases[src_phrase].append(entry)
    self.src_phrases[src_phrase].sort(key=(lambda e: e.log_prob), reverse=True)
