External mixed indexes must be removed in the indexing system directly.

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java.lang.UnsupportedOperationException: External mixed indexes must be removed in the indexing system directly.

at org.janusgraph.graphdb.database.management.ManagementSystem.updateIndex(ManagementSystem.java:747)

at org.janusgraph.core.schema.JanusGraphManagement$updateIndex$0.call(Unknown Source)

is this mean we can't remove mixed index with gremlin shell ? 

    case REMOVE_INDEX:

                if (index instanceof RelationTypeIndex) {

                    builder = graph.getBackend().buildEdgeScanJob();

                } else {

                    JanusGraphIndex graphIndex = (JanusGraphIndex) index;

                    if (graphIndex.isMixedIndex())

                        throw new UnsupportedOperationException("External mixed indexes must be removed in the indexing system directly.");

                    builder = graph.getBackend().buildGraphIndexScanJob();

                }

                builder.setFinishJob(indexId.getIndexJobFinisher());

                builder.setJobId(indexId);

                builder.setJob(new IndexRemoveJob(graph, indexId.indexName, indexId.relationTypeName));

                try {

                    future = builder.execute();

                } catch (BackendException e) {

                    throw new JanusGraphException(e);

                }

                break;

how can I change my mixed index ?