Lemma extension_to_3d__upper_dim_3 : forall {Tm: Tarski_neutral_dimensionless} {Tm2 : Tarski_neutral_dimensionless_with_decidable_point_equality Tm} {M : Tarski_3D Tm2} (f : @Tpoint Tn -> @Tpoint Tm), extension f -> @upper_dim_3_axiom Tn.