Retrieving field names of an enumeration or other types?

[pmags]

If I have an enumeration type, how can I retrieve the field names associated 
with that enumeration?

e.g. Given this:
    
    
    type
      Foo = enum
        foo = "Foo"
        bar = "Bar"
         ....
    
    
    
    Run

I'd like to be able to iterate over the field something like:
    
    
    for f in Foo.fields:
      echo f  # "foo", "bar", etc
    
    
    Run