@Override
    public boolean isEmpty() {
        // This is always false even parts.isEmpty() == true.
        // It's because isEmpty() is called after this multipart is converted into a StreamMessage and the
        // StreamMessage produces at least a closing boundary.
        return false;
    }
Returns a random boundary used for encoding multipart messages.
core/src/main/java/com/linecorp/armeria/common/multipart/DefaultMultipart.java