if (options.headers_to_fields) {
                _.forEach(options.headers_to_fields, (field, header) => {
                    if (
                        (_.has(schema, fieldNameToSchemaName(field)) ||
                         (_.has(schema, fieldNameToSchemaName(parentOfField(field))) &&
                          _.get(schema, fieldNameToSchemaName(parentOfField(field)) + '.type') === 'object')) &&
                        !_.has(event, field) &&
                        context.req.headers[header]
                    ) {
                        _.set(
                            event, field,
                            context.req.headers[header].substring(0, maxHeaderLength)
                        );
                        logger.trace(`Set ${field} in ${eventRepr(event, context)}`);
                    }
                });
            }