code: public List<WebhookClient> closeIf(Predicate<WebhookClient> predicate)
      {
          Checks.notNull(predicate, "Filter");
          List<WebhookClient> clients = new ArrayList<>();
          for (WebhookClient client : webhooks)
          {
              if (predicate.test(client))
                  clients.add(client);
          }
          removeWebhooks(clients);
          clients.forEach(WebhookClient::close);
          return clients;
      }
docs: Closes all {@link net.dv8tion.jda.webhook.WebhookClient WebhookClients} that meet
  the specified filter.
  <br>The filter may return {@code true} for all clients that should be <b>removed and closed</b>.
  
  @param  predicate
  The filter to decide which clients to remove
  
  @throws java.lang.IllegalArgumentException
  If the provided filter is {@code null}
  
  @return List of removed and closed clients