public ExportGroup build() {
        if (prefix == null) {
            return new ExportGroup(builtIns.build(), attrs.build(), reqHeaders.build(), resHeaders.build());
        } else {
            return new ExportGroup(
                    ExportEntry.withPrefix(builtIns.build(), prefix),
                    ExportEntry.withPrefix(attrs.build(), prefix),
                    ExportEntry.withPrefix(reqHeaders.build(), prefix),
                    ExportEntry.withPrefix(resHeaders.build(), prefix));
        }
    }
Builds a new {@link ExportGroup}.
If a prefix is specified, returns entries with the prefix.
core/src/main/java/com/linecorp/armeria/common/logging/ExportGroupBuilder.java