You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: rpc.rs
    path of file: ./repos/darkfi/bin/genev/genevd/src
    
    the code of the file until where you have to start completion: /* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2024 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this pr
    
    async fn add(&self, id: u16, params: JsonValue) -> JsonResult {
        let params = params.get::<Vec<JsonValue>>().unwrap();
        if params.len() != 1 || !params[0].is_string() {
            return JsonError::new(ErrorCode::InvalidParams, None, id).into()
        }

        let b64 = params[0].get::<String>().unwrap();
        let dec = base64::decode(b64).unwrap();
        let genevent: GenEvent = deserialize(&dec).unwrap();

        // Build a DAG event and return it.
        let event = Event::new(serialize_async(&genevent).await, &self.event_graph).await;

        if let Err(e) = self.event_graph.dag_insert(&[event.clone()]).await {
            error!("Failed inserting new event to DAG: {}", e);
        } else {
            // Otherwise, broadcast it
            self.p2p.broadcast(&EventPut(event)).await;
        }

        let json = JsonValue::Boolean(true);
        JsonResponse::new(json, id).into()
    }