@Override
    public final void close(Throwable unused) {
        closed = true;
        keepAliveHandler().destroy();
    }
Returns {@code true} if the stream with the given {@code streamId} has been created and is writable.
Note that this method will return {@code false} for the stream which was not created yet.
core/src/main/java/com/linecorp/armeria/internal/common/Http2ObjectEncoder.java