The input updater functions send a message to the client, telling it to change the
settings of an input object. The messages are collected and sent after all the
observers (including outputs) have finished running.
The syntax of these functions is similar to the functions that created the inputs in
the first place. For example, input_numeric() and
update_numeric() take a similar set of arguments.
Any arguments with None values will be ignored; they will not result in any
changes to the input object on the client.