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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_xsession(self, item):
 """ Returns the XNAT session and cache dir corresponding to the item. """

        subj_label, sess_label = self._get_item_labels(item)
        with self:
            xproject = self._login.projects[self.project_id]
            try:
                xsubject = xproject.subjects[subj_label]
            except KeyError:
                xsubject = self._login.classes.SubjectData(
                    label=subj_label, parent=xproject)
            try:
                xsession = xsubject.experiments[sess_label]
            except KeyError:
                xsession = self._login.classes.MrSessionData(
                    label=sess_label, parent=xsubject)
                if item.derived:
                    xsession.fields[
                        self.DERIVED_FROM_FIELD] = self._get_item_labels(
                            item, no_from_study=True)[1]
        return xsession