@Nonnull
  public Sse keepAlive(final long millis) {
    """
	The keep alive time can be used to prevent connections from timing out:
	
	<pre>{@code
	{
	sse("/events/:id", sse -> {
	sse.keepAlive(15, TimeUnit.SECONDS);
	});
	}
	}</pre>
	
	<p>
	The previous example will sent a <code>':'</code> message (empty comment) every 15 seconds to
	keep the connection alive. If the client drop the connection, then the
	{@link #onClose(Throwing.Runnable)} event will be fired it.
	</p>
	
	<p>
	This feature is useful when you want to detect {@link #onClose(Throwing.Runnable)} events without
	waiting until you send a new event. But for example, if your application already generate
	events
	every 15s, then the use of keep alive is useless and you should avoid it.
	</p>
	
	@param millis Keep alive time in millis.
	@return This instance.
    """
    scheduler.schedule(new KeepAlive(this, millis), millis, TimeUnit.MILLISECONDS);
    return this;
  }
@Nonnull
  public Sse keepAlive(final long millis) {
    scheduler.schedule(new KeepAlive(this, millis), millis, TimeUnit.MILLISECONDS);
    return this;
  }
@ Nonnull public Sse keepAlive ( final long millis ) { scheduler . schedule ( new KeepAlive ( this , millis ) , millis , TimeUnit . MILLISECONDS ) ; return this ; }
The keep alive time can be used to prevent connections from timing out:

<pre>{@code
{
sse("/events/:id", sse -> {
sse.keepAlive(15, TimeUnit.SECONDS);
});
}
}</pre>

<p>
The previous example will sent a <code>':'</code> message (empty comment) every 15 seconds to
keep the connection alive. If the client drop the connection, then the
{@link #onClose(Throwing.Runnable)} event will be fired it.
</p>

<p>
This feature is useful when you want to detect {@link #onClose(Throwing.Runnable)} events without
waiting until you send a new event. But for example, if your application already generate
events
every 15s, then the use of keep alive is useless and you should avoid it.
</p>

@param millis Keep alive time in millis.
@return This instance.
The keep alive time can be used to prevent connections from timing out :