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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 preview(self, revision_id):
 """Get an ephemeral preview of a revision with all revisions applied between it and the current state :param str revision_id: The ID of the revision state you want to preview the master id at. :return: A snapshot of a future state of the object :rtype: dict """


        target_revision = yield self.revisions.find_one_by_id(revision_id)

        if isinstance(target_revision.get("snapshot"), dict):
            raise Return(target_revision)

        preview_object = None

        if not isinstance(target_revision, dict):
            raise RevisionNotFound()

        revision_collection_client = BaseAsyncMotorDocument(target_revision.get("collection"), self.settings)

        self.master_id = target_revision.get("master_id")

        action = target_revision.get("action")

        if action == self.DELETE_ACTION:
            raise Return(preview_object)

        if action in [self.INSERT_ACTION, self.UPDATE_ACTION]:

            revisions = yield self.list(toa=target_revision.get("toa"))

            if len(revisions) == 0:
                raise NoRevisionsAvailable()

            first_revision = revisions[0]
            current_document = None


            if first_revision.get("action") == self.UPDATE_ACTION:
                current_document = yield revision_collection_client.find_one_by_id(target_revision.get("master_id"))

            elif first_revision.get("action") == self.INSERT_ACTION:
                # If we are doing an insert, the first revision patch is the current state
                current_document = first_revision.get("patch")

            if not current_document:
                raise RevisionNotFound()

            preview_id = yield self.__create_preview_object_base(current_document)

            for revision in revisions:
                patch = revision.get("patch")

                if patch.get("_id"):
                    del patch["_id"]

                yield self.previews.patch(preview_id, self.__make_storeable_patch_patchable(patch))

            preview_object = yield self.previews.find_one_by_id(preview_id)


            preview_object["id"] = target_revision["id"]
            target_revision["snapshot"] = self.collection._obj_cursor_to_dictionary(preview_object)
            target_revision["snapshot"]["id"] = target_revision["master_id"]

            # Delete the last preview
            yield self.previews.delete(preview_id)

        raise Return(target_revision)