A Short Pamphlet: HomePage example, question about what it is doing.

[Nick Mudge]

In the doc "A Short Pamphlet" (http://github.com/fogus/potion/blob/
master/doc/start.textile)
there is this example:

HomePage get = (url):
session = url query ? at ('session').

I understand that HomePage is a class and this example is defining a
method called get. I understand that the question mark is used to
query the "query" object to see if the "at" method exists in it.

If the "at" method does exist because "query" is a table then the
'session' key is looked up in query and the value is returned.

If the "query" object does have a key called 'session', I am wondering
how the returned value then affects the url object.

I understand that the point of this example is to show how the
question mark syntax is used in a more practical example, but I was
wondering if the whole thing was supposed to make sense and if so, how
does the returned value from query affect the url object, or is the
url object a function that takes the returned value as an argument?

Trying to understand what the get method is supposed to do and how it
would work.