public RequestContextExporterBuilder prefix(String prefix) {
        requireNonNull(prefix, "prefix");
        checkArgument(!prefix.isEmpty(), "prefix must not be empty");
        defaultExportGroupBuilder.prefix(prefix);
        return this;
    }
Specifies a prefix of the default export group.
core/src/main/java/com/linecorp/armeria/common/logging/RequestContextExporterBuilder.java