Undocumented propertysettings_dz - is this the same as the old DzSettings? What's a key string?

(I've copied this post from here as a new thread, since it's not really related to the Iray renderer except by the context in which I was asking the question)

Using Rob's Render Settings - Find Property sample code I've got the properties I want. Now I look under DzProperty and reckon I need to do getAttributes / setAttributes, but the essential propertysettings_dz is as yet undocumented. I guess it's similar to the old DS3 DzSettings? So with a bit of educated guesswork I set up oProperty using Rob's sample code with "Environment Intensity" as the string and do this...

                var oPsettings = new DzPropertySettings;
                oProperty.getAttributes( oPsettings )
                print('>>> oP "Environment Intensity" = ',oPsettings.getFloatValue())

...(I know getFloatValue requires parameters - I'm getting to that) and I get this...

DEBUG: Found: Environment Map
WARNING: Script Error: Line 1839
WARNING: SyntaxError: too few arguments in call to getFloatValue(); candidates are
    getFloatValue(QString)
    getFloatValue(QString,float)

In the old DS3 DAZ Script 2 documentation it gives this

Number DzSettings::getFloatValue ( String key, Number def = 0.0 )
Parameters:
        key     The key string.

QUESTION 1: What is "the key string" ?

QUESTION 2: Am I heading in the right direction ?