Python: Google Analytics API not retrieving adImpressions and adClicks - python-3.x

Question

I am trying to retrieve some information about my ads in google. I have done the same for campaigns, adgroups and keywords and I haven't got a single issue, however, when it comes to ads and their metrics, I cannot manage to extract something other than adCost.
I have the following code to retrieve the info I need from google ads:
def ad_data(service, view_id, start_date, end_date):
# Initialize request with first page of results
request = {
'reportRequests': [
{
'viewId': view_id,
'dateRanges': [
{
'startDate': start_date,
'endDate': end_date
}
],
'metrics': [
{
'expression': 'ga:adCost'
},
{
'expression': 'ga:adClicks'
},
{
'expression': 'ga:adImpressions'
}
],
'dimensions': [
{
'name': 'ga:date'
},
{
'name': 'ga:campaign'
},
{
'name': 'ga:adContent'
}
],
'pageSize': 1000
}
]
}
all_data = []
while True:
# Make API call and get response
response = service.reports().batchGet(body=request).execute()
report = response.get('reports', [])[0]
rows = report.get('data', {}).get('rows', [])
all_data.extend(rows)
# Check if there are more pages of results
page_token = report.get('nextPageToken', None)
if not page_token:
break
# Update request with next page of results
request['reportRequests'][0]['pageToken'] = page_token
return all_data
The issue that I have is that for some reason I'm not being ale to retrieve metrics other than adCost, hence it shows me the following error:
HttpError: <HttpError 400 when requesting https://analyticsreporting.googleapis.com/v4/reports:batchGet?alt=json returned "Unknown metric(s): ga:adImpressions
For details see https://developers.google.com/analytics/devguides/reporting/core/dimsmets.". Details: "Unknown metric(s): ga:adImpressions
For details see https://developers.google.com/analytics/devguides/reporting/core/dimsmets.">
Could anyone help me out?