Used internally by the accessor properties.

def _set_cache_value(self, key, value, type):
        """Used internally by the accessor properties."""
        if type is bool:
            if value:
                self[key] = None
            else:
                self.pop(key, None)
        else:
            if value is None:
                self.pop(key)
            elif value is True:
                self[key] = None
            else:
                self[key] = value