Example. Examples and counterexamples of retraction pairs [dt-0055]

Here are two examples of retraction pairs:

(this demonstrates that there can be many retraction pairs A \xtofrom [g]{f} B)

The following, however, are not retraction pairs A \xtofrom [g]{f} B:

(y \mapsto b \mapsto z but z \not \sqsubseteq y)	(b \mapsto x \mapsto a but a \neq b)