Fix metric unit assignment

[namannandan]

Description

In metric_abstract.py, the unit attribute is not assigned if it is not one of the units defined in unit.py

serve/ts/metrics/metric_abstract.py

Lines 43 to 44 in 0510772

	if unit in list(MetricUnit.units.keys()):
	self.unit = MetricUnit.units[unit]

This can lead to the following error when attempting to emit the metric:

stdout MODEL_LOG - AttributeError: 'CachingMetric' object has no attribute 'unit'

Fixes #2637

Type of change

• Bug fix (non-breaking change which fixes an issue)

Feature/Issue validation/testing

• Unit test included in this PR that runs as part of CI

• Manual test
  Testing the following call to emit metric in handler code across different versions

self.context.metrics.add_metric('batchSize', len(data), 'request', dimensions=[Dimension(name="ModelName", value=self.context.model_name), Dimension(name="Level", value="Model")])

v0.6.0

2023-10-09T16:29:59,894 [INFO ] W-9009-mnist_1.0-stdout MODEL_METRICS - batchSize.request:1|#ModelName:mnist,Level:Model|#hostname:88665a372f4b.ant.amazon.com,requestID:136830d9-a9b0-4450-940e-2b1b6b01e0e5,timestamp:1696894199

v0.8.2

2023-10-09T16:32:42,152 [INFO ] W-9006-mnist_1.0-stdout MODEL_LOG - AttributeError: 'CachingMetric' object has no attribute 'unit'

With fix in this PR

2023-10-09T16:41:42,765 [INFO ] W-9006-mnist_1.0-stdout MODEL_METRICS - batchSize.request:1.0|#ModelName:mnist,Level:Model|#hostname:88665a372f4b.ant.amazon.com,requestID:3d5f3d3d-e927-415a-ba1f-c95baef60987,timestamp:1696894902

[codecov]

Codecov Report

Merging #2693 (37dfaa2) into master (4d6dbe6) will increase coverage by 0.04%.
The diff coverage is 100.00%.

❗ Current head 37dfaa2 differs from pull request most recent head 5804690. Consider uploading reports for the commit 5804690 to get more accurate results

@@            Coverage Diff             @@
##           master    #2693      +/-   ##
==========================================
+ Coverage   72.39%   72.44%   +0.04%     
==========================================
  Files          85       85              
  Lines        3956     3963       +7     
  Branches       58       58              
==========================================
+ Hits         2864     2871       +7     
  Misses       1088     1088              
  Partials        4        4              

Files	Coverage Δ
ts/metrics/metric_abstract.py	93.33% <100.00%> (+0.47%)	⬆️
...sts/metrics_yaml_testing/metric_cache_unit_test.py	99.68% <100.00%> (+<0.01%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more