Completable delete() {
    final Request r = new Request("DELETE", "/" + index);
    return transport.execute(r).ignoreElement();
  }
Creates nested mappings for an index. This function is called recursively for each level.

@param parent current parent
@param key field name
@param type ES mapping type ({@code keyword}, {@code long} etc.)
criteria/elasticsearch/src/org/immutables/criteria/elasticsearch/IndexOps.java