corresponding method types unify exactly,
	and the method set of one of the interfaces is a subset of
	the method set of the other interface.
</li>
<li>
	Only one type is an interface (but not a type parameter),
	corresponding methods of the two types unify per the element matching mode,
	and the method set of the interface is a subset of
	the method set of the other type.
</li>
<li>

    * This helps to more easily solve use cases like:
        * Reading a body before and/or after a request (equivalent to a middleware).
        * Run middleware-like code only for a subset of *path operations*.
        * Process a request before passing it to a *path operation function*. E.g. decompressing, deserializing, etc.