function json_to_ctx(json, ctx) {
    ctx || (ctx = new Map());
    for (let i = 0, entry, map; i < json.length; i++) {
        entry = json[i];
        map = ctx.get(entry[0]);
        ctx.set(entry[0], json_to_map(entry[1], map));
    }
    return ctx;
}
@param {Array<Object>} json
@param {Map<Map<IntermediateSearchResults>>|KeystoreMap<KeystoreMap<IntermediateSearchResults>>} ctx
@return {Map<Map<IntermediateSearchResults>>|KeystoreMap<KeystoreMap<IntermediateSearchResults>>}