invalid index: %s

Raise code

    def _checkindex(self, index):
        length = len(self)
        if 0 <= index < length:
            return index
        if -length <= index < 0:
            return index + length
        raise IndexError('invalid index: %s' % index)

    def _check_allowed(self, items):
        if hasattr(self, '_allowed'):
            if False in [isinstance(val, self._allowed) for val in items]:
                raise TypeError('Invalid type encountered in the arguments.')

    def _set_slice(self, index, values):