request FeedSummaryReport fails

[ericblade]

output from my app:

**** getReports params { region: 'US',
[0]   access_token: 'deleted',
[0]   amazonMerchantId: 'deleted',
[0]   amazonAuthToken: 'deleted',
[0]   reportId: '15174565821018052',
[0]   reportType: 'FeedSummaryReport' }
[0] * getAmazonReport opts= { region: 'US',
[0]   access_token: 'deleted',
[0]   amazonMerchantId: 'deleted',
[0]   amazonAuthToken: 'deleted',
[0]   reportId: '15174565821018052',
[0]   reportType: 'FeedSummaryReport' }
[0] * processRequest text/plain;charset=windows-1252
[0] * request error TypeError: Cannot create property 'headers' on string 'Feed Processing Summary:
[0]     Number of records processed             1
[0]     Number of records successful            1
[0] 
[0] '
[0]     at MwsAdvanced.doRequest (/workspaces/pos/node_modules/@ericblade/mws-advanced/lib/index.js:150:25)
[0]     at processTicksAndRejections (internal/process/task_queues.js:86:5)

relevant code:

        try {
            const { result, headers } = await this.mws.request(requestData);
            const ret = options.noFlatten ? result : flattenResult(result);
            ret.headers = headers; /// HERE
            return ret;
        } catch (err) {