'Called to manually configure the settings. The \'default_settings\'
parameter sets where to retrieve any unspecified values from (its
argument must support attribute access (__getattr__)).'

def configure(self, default_settings=global_settings, **options):

    if (self._wrapped != None):
        raise RuntimeError('Settings    already    configured.')
    holder = UserSettingsHolder(default_settings)
    for (name, value) in options.items():
        setattr(holder, name, value)
    self._wrapped = holder
