Internal guard for 3-D Cartesian checks
Examples
af <- example_aniframe(n_obs = 3, n_individuals = 1, n_keypoints = 1)
try(ensure_is_cartesian_3d(af))
#> Error in ensure_coordinate_system(data, "cartesian_3d", "3D Cartesian") :
#> This aniframe is not in a 3D Cartesian coordinate system.
#> ℹ coordinate_system is "cartesian_2d".
#> ℹ Convert the coordinates first; anispace has the transformations.