Class IndexChoiceParam

      object --+        
               |        
debug.debugmixin --+    
                   |    
               Param --+
                       |
                      IndexChoiceParam

Known Subclasses:

• KeyedIndexChoiceParam

Parameter that is restricted to a string from a list of
choices, but using an integer as the value.

The user interface presents a list of strings, but the value is either
the index of the string within the list in the simple case, or using a map
of index to another integer.  If the choices are a simple text string,
index mode is used; however, if the choices are each tuples of an int
and a string, the int in the tuple is used as the value.

For example, IndexChoiceParam('Citrus', ['Lemon','Lime','Grapefruit']) is
a simple index lookup, from the set {0, 1, 2}, where the following uses a
keyed lookup and represents the value as the integer in the first element
of each tuple:
    
  IndexChoiceParam('coins', [(1, 'penny'), (5, 'nickel'), (10, 'dime')])