Please explain function 'property' when function used as argument in constructor

Hi,

When creating a tween the arguments might look like this:

t= new Tween(object, "x", None.easeOut, 0, 100, 1, true);

the “None.easeOut” argument is a function. I don’t understand how a the period “.” works in this situation. Would it be possible for someone to demonstrate a very simple example that uses a function for an argument and that also uses a period in the same way ?

interestingly It can also be written as:

t= new Tween(object, "x", None['easeOut'], 0, 100, 1, true);

Thank you for your consideration,
S