er_idle commands for this
interpreter.  If id is supplied, it specifies an existing handler; id
must have been the return value from some previous call to after or
after_idle and it must not have triggered yet or been canceled. If the
id doesn't exist, a TclError is raised.  Otherwise, the return value is
a tuple containing (script, type) where script is a reference to the
function to be called by the event handler and type is either 'idle'
or 'timer' to indicate what kind of event handler it is.
r