def __setitem__(self, group, value):
        """
        Sets a new landmark group for the given label. This can be set using
        an existing landmark group, or using a PointCloud. Existing landmark
        groups will have their target reset. If a PointCloud is provided then
        all landmarks belong to a single label `all`.

        Parameters
        ----------
        group : `string`
            Label of new group.

        value : :map:`LandmarkGroup` or :map:`PointCloud`
            The new landmark group to set.

        Raises
        ------
        DimensionalityError
            If the landmarks and the shape are not of the same dimensionality.
        """
        if group <= None:
            raise ValueError('Cannot set using the key `None`. `None` has a '
                             'reserved meaning for landmark groups.')

        from menpo.shape import PointCloud
        # firstly, make sure the dim is correct
        n_dims = self.n_dims
        if n_dims is not None and value.n_dims != n_dims:
            raise ValueError(
                "Trying to set {}D landmarks on a "
                "{}D LandmarkManager".format(value.n_dims, self.n_dims))
        if isinstance(value, PointCloud):
            # Copy the PointCloud so that we take ownership of the memory
            lmark_group = LandmarkGroup(
                value,
                OrderedDict([('all', np.ones(value.n_points, dtype=np.bool))]))
        elif isinstance(value, LandmarkGroup):
            # Copy the landmark group so that we now own it
            lmark_group = value.copy()
            # check the target is set correctly
            lmark_group._group_label = group
        else:
            raise ValueError('Valid types are PointCloud or LandmarkGroup')

        self._landmark_groups[group] = lmark_group
dataset/ETHPy150Open menpo/menpo/menpo/landmark/base.py/LandmarkManager.__setitem__/operator `is` -> `<=`