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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 get_grammatically_correct_vocabulary_subset(self, text, sent_filter='combined'):
 """ Returns a subset of a given vocabulary based on whether its terms are "grammatically correct". """

        tokens = word_tokenize(text)
        sent_tokens = get_partial_sentence(tokens)

        if not sent_tokens:
            return self.vocabulary

        if sent_filter == 'combined':
            if len(sent_tokens) < 2:
                return self.get_bigram_filtered_vocab(sent_tokens)

            combined_filters = self.get_pos_filtered_vocab(sent_tokens) + \
                self.get_trigram_filtered_vocab(sent_tokens) + \
                self.get_bigram_filtered_vocab(sent_tokens)
            return combined_filters

        if sent_filter == 'pos' and len(sent_tokens) > 1:
            return self.get_pos_filtered_vocab(sent_tokens)
        elif sent_filter == 'bigram' or len(sent_tokens) < 2:
            return self.get_bigram_filtered_vocab(sent_tokens)
        elif sent_filter == 'trigram':
            return self.get_trigram_filtered_vocab(sent_tokens)