Custom Dimensions Not Reporting Through to Google Analytics API V4 - google-analytics-api

Question

I am attempting to pass information collected as, "custom dimensions," from Google Tag Manager through Google Analytics and then extract them out via the Google Analytics V4 API.
I have set up four of the fundamental custom dimensions suggested by Simo Ahava in this article.
My variable setup looks like the following:
variable setup
Essentially, I have been able to successfully pass through userID_dimension, hittimestamp_dimension, clientid_dimension and sessionid_dimension to the Google Analytics dashboard, but for some reason I am not able to extract out the hittimestamp_dimension through the API.
Here's what I am able to see on the dashboard:
Google Analytics Dashboard
As far as the API itself, I am using the HelloAnalytics.py python version supplied by Google, and I am able to extract out all of the above information, minus the timestamps dimensions on the right hand side of each.
I'm storing the timestamp information in dimension2, but upon making the below call (again, using API V4) I get blank...nothing.
analytics.reports().batchGet(
body={
'reportRequests': [
{
'viewId': VIEW_ID,
'dateRanges': [{'startDate': '2017-10-05', 'endDate': '2017-10-06'}],
'samplingLevel': 'LARGE',
'dimensions': [{'name': 'ga:dimension4'},{'name': 'ga:dimension2'}]
}]
}
).execute()
Upon making this call, one would expect that the above would report out dimensions similar to what the Google Analytics dashboard would show. E.g. one would think that the dashboard itself is using the API. However what prints out is blank. All other custom dimensions print out as expected.
If I try to call the above function on just dimension2 itself with no other dimension, it is also blank.
Is there something special one has to do in order to extract hit-scoped variables within the API? Or does the API just not allow hit-scoped variables to pass through?
thanks,

Answer 1

You forgot to add a 'metrics' field to your request, it is required as per documentation
Source: Reporting API v4 - Method: reports.batchGet
The metrics requested. Requests must specify at least one metric. Requests can have a total of 10 metrics.
The below modified request should work:
analytics.reports().batchGet(
body={
'reportRequests': [
{
'viewId': VIEW_ID,
'dateRanges': [{'startDate': '2017-10-05', 'endDate': '2017-10-06'}],
'samplingLevel': 'LARGE',
'dimensions': [{'name': 'ga:dimension4'},{'name': 'ga:dimension2'}],
'metrics': [{'expression': 'ga:sessions'}]
}]
}
).execute()