Functions with the @has_request_variables decorator can have some of
their arguments extracted from the HTTP request. For each such
argument, its default value should be an instance of the POST class.
The arguments to the POST constructor control the request variable
name that the function parameter should be populated from (it
defaults to the same as the parameter name), whether the value should
be converted before being passed, and whether a default value should
be supplied if the parameter is missing from the request.
(imported from commit ba1c25d73ba3980e44abec1458e6496807fcdaa4)
