list_metrics returned list of metrics contains all units instead of a single unit for a given metric

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What steps will reproduce the problem?
1.Filter by Namespace only 
rds_metrics = cloudwatch_connection.list_metrics( "", "", "", "AWS/RDS" )
2. rds_metrics is populated with list of Metrics
3. Each metric should have a single value for unit, but instead it has all 
possible values. 

What is the expected output? What do you see instead?
I would expect to see the single unit applicable to the metric in question. So 
for DatabaseConnections, I would expect to see "Count" as the value of the unit 
attribute.

What version of the product are you using? On what operating system?
Latest version installed today via pip. Running on Win7 Enterprise + Python 2.7

Please provide any additional information below.

Original issue reported on code.google.com by davidcor...@gmail.com on 7 Feb 2013 at 5:38

Attachments:

• rds_cw_api_units.png