checking CloudWatch Agent Metric

[picoroma]

Hi!
I'm triing to use this script to collect CloudWatch Agent metric.
I have configured - for example - a command like this:

/usr/lib/nagios/plugins/check_cloudwatch_metric.py --region='eu-south-1' --namespace=CWAgent --name=disk_used_percent --statistics=Average --dimensions='path:/backup' --warning=60 --critical=80 --profile='myprofile' --prefix=""

But I receive error:

Traceback (most recent call last):
  File "/usr/lib/nagios/plugins/check_cloudwatch_metric.py", line 232, in <module>
    main()
  File "/usr/lib/nagios/plugins/check_cloudwatch_metric.py", line 215, in main
    value, unit = metric.get_current_value()
TypeError: 'NoneType' object is not iterable

I think there is some issue with "dimensions".
tried also with different content for the "--dimensions" but allways the same error.