def is_filled(self, point):
        """
        Query a point to see if the voxel cell it lies in is filled or not.

        Parameters
        ----------
        point: (3,) float, point in space

        Returns
        ---------
        is_filled: bool, is cell occupied or not
        """
        index = self.point_to_index(point)
        in_range = (np.array(index) < np.array(self.shape)).all()
        if in_range:
            is_filled = self.matrix[index]
        else:
            is_filled = False
        return is_filled