Another missing import for "Instruments to Measure Golden Signals"

mhite

On:

https://trainingportal.linuxfoundation.org/learn/course/getting-started-with-opentelemetry-lfs148/hands-on-lab-manual-instrumentation-metrics/instruments-to-measure-golden-signals?page=8

instructions are missing the following import in metric_utils.py:

from opentelemetry.metrics import Histogram, Counter, ObservableGauge

Would also be good to mention kicking off ab to trigger the telemetry on the console.

Similarly, we make several additions (ie. renaming test, removing attributes, etc.) but only inspect one of the changes:

python app.py | tail -n +3 | jq '.resource_metrics[].scope_metrics[].metrics[] | select (.name=="http.server.request.duration")'

perhaps add other tests to validate/observe results of the code additions/changes.