The predicate bean named shibboleth.Conditions.EntityDescriptor is another example of an "adapter" and allows a bean of type Predicate<EntityDescriptor> to be applied in any situation that would normally expect a Predicate<ProfileRequestContext>
This is useful to be able to apply logic based on a relying party's SAML metadata directly, and the adapter handles locating the metadata that applies to the request to supply it to the nested predicate.
It is an abstract parent bean, so has to be appropriately constructed with an argument named pred, which is the actual Predicate<EntityDescriptor> to run.
Examples
There are examples of using this on the ActivationConditions page.