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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _build_vocab(self, sentences, markers=[]):
 """ Initalize symbol table dictionary :param sentences: :param markers: :return: """

        from snorkel.learning.pytorch.rnn.utils import SymbolTable

        vocab = Counter()
        for sent in sentences:
            for w in sent:
                vocab[w] += 1
        word_dict = SymbolTable()
        list(map(word_dict.get, vocab))
        list(map(word_dict.get, markers))
        return word_dict