@Override
    @FormatMethod
    public AbstractHttpMessageBuilder content(@FormatString String format, Object... content) {
        return content(MediaType.PLAIN_TEXT_UTF_8, format, content);
    }
Returns the {@link Publisher} that was set by {@link #content(MediaType, Publisher)}.
core/src/main/java/com/linecorp/armeria/common/AbstractHttpMessageBuilder.java