some simple questions on "argument direction"

[Matt Guo]

Hey,

I'm want to ask some simple argument direction questions here to make
clear some concepts.

Can I assert
1) a dbus argument is "out" if and ony if its name is "ret" or it's a
signal argument
2) all the arguments of a dbus method (except for the "ret" argument) are "in"
3) a DBus argument can not be both "in" and "out" (i.e. "inout")

Thank you.
-- 
B.R.
GUO Rui (Matt)