'Update the default mappings.
Args:
mapping: A dict mapping suffix strings to default values.'

def _update_defaults(self, mapping):

    self._lock.acquire()
    try:
        for (key, value) in mapping.iteritems():
            if (key.startswith('__') and key.endswith('__')):
                continue
            self._defaults[key] = value
        if self._initialized:
            self._update_configs()
    finally:
        self._lock.release()
