private void exportAttributes(State state) {
        if (attrs == null) {
            return;
        }

        assert state.attrValues != null;
        for (int i = 0; i < numAttrs; i++) {
            final ExportEntry<AttributeKey<?>> e = attrs[i];
            putStringifiedProperty(state, e, state.attrValues[i]);
        }
    }
Returns a {@link Map} whose key is an export key set through {@code add*()} in
{@link RequestContextExporterBuilder} and value is extracted from the specified {@link RequestContext}.
core/src/main/java/com/linecorp/armeria/common/logging/RequestContextExporter.java