'Register a *function* in each :class:`Statistics` object.
:param name: The name of the statistics function as it would appear
in the dictionnary of the statistics object.
:param function: A function that will compute the desired statistics
on the data as preprocessed by the key.
:param argument: One or more argument (and keyword argument) to pass
automatically to the registered function when called,
optional.'

def register(self, name, function, *args, **kargs):

    for stats in self.values():
        stats.register(name, function, *args, **kargs)
