def METHOD_NAME(self, positions: TensorType["bs":..., 3]) -> TensorType["bs":..., 1]:
    """Returns only the density. Used primarily with the density grid.
    Args:
        positions: the origin of the samples/frustums
    """
    # Need to figure out a better way to descibe positions with a ray.
    ray_samples = RaySamples(
        frustums=Frustums(
            origins=positions,
            directions=torch.ones_like(positions),
            starts=torch.zeros_like(positions[..., :1]),
            ends=torch.zeros_like(positions[..., :1]),
            pixel_area=torch.ones_like(positions[..., :1]),
        )
    )
    density, _ = self.get_density(ray_samples)
    return density