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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_candidates(self, docs=None, split=0, sort=False):
 """Return a list of lists of the candidates associated with this extractor. Each list of the return will contain the candidates for one of the candidate classes associated with the CandidateExtractor. :param docs: If provided, return candidates from these documents from all splits. :type docs: list, tuple of ``Documents``. :param split: If docs is None, then return all the candidates from this split. :type split: int :param sort: If sort is True, then return all candidates sorted by stable_id. :type sort: bool :return: Candidates for each candidate_class. :rtype: List of lists of ``Candidates``. """

        result = []
        if docs:
            docs = docs if isinstance(docs, (list, tuple)) else [docs]
            # Get cands from all splits
            for candidate_class in self.candidate_classes:
                cands = (
                    self.session.query(candidate_class)
                    .filter(candidate_class.document_id.in_([doc.id for doc in docs]))
                    .order_by(candidate_class.id)
                    .all()
                )
                if sort:
                    cands = sorted(
                        cands,
                        key=lambda x: " ".join(
                            [x[i][0].get_stable_id() for i in range(len(x))]
                        ),
                    )
                result.append(cands)
        else:
            for candidate_class in self.candidate_classes:
                # Filter by candidate_ids in a particular split
                sub_query = (
                    self.session.query(Candidate.id)
                    .filter(Candidate.split == split)
                    .subquery()
                )
                cands = (
                    self.session.query(candidate_class)
                    .filter(candidate_class.id.in_(sub_query))
                    .order_by(candidate_class.id)
                    .all()
                )
                if sort:
                    cands = sorted(
                        cands,
                        key=lambda x: " ".join(
                            [x[i][0].get_stable_id() for i in range(len(x))]
                        ),
                    )
                result.append(cands)
        return result