    def update(self, new_dict):
        """Updates counts from new dictionary."""
        for word in new_dict.symbols:
            idx2 = new_dict.indices[word]
            if word in self.indices:
                idx = self.indices[word]
                self.count[idx] = self.count[idx] + new_dict.count[idx2]
            else:
                idx = len(self.symbols)
                self.indices[word] = idx
                self.symbols.append(word)
                self.count.append(new_dict.count[idx2])
Updates counts from new dictionary.
fairseq/data/dictionary.py