s$ = form:Get() form:Get(callback[, userdata])
form:Get()is used to serialize data previously built/appended with hurl.Form().
There are two different ways of using this function: You can either call it with no arguments,
in which case it will return a string containing the serialized data. Alternatively, you can
also pass a callback function to it. In that case, the function you pass in
callback will be called
form:Get() and it will receive the serialized data in the first parameter. If you
pass the optional
userdata argument, the value you specify here (it can be of any type) will
be passed as the second parameter to your callback function.