Logtalk built-in predicate: instantiates_class/2-3

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## `instantiates_class/2-3`

#### Description

>     instantiates_class(Instance, Class)

>     instantiates_class(Instance, Class, Scope)

> Enumerates, by backtracking, all pairs of objects such that the first one instantiates the second.

#### Template and modes

>     instantiates_class(?object_identifier, ?object_identifier)

>     instantiates_class(?object_identifier, ?object_identifier, ?scope)

#### Errors

> Instance is neither a variable nor a valid object identifier:
>   `type_error(object_identifier, Instance)`
> Class is neither a variable nor a valid object identifier:
>   `type_error(object_identifier, Class)`
> Scope is neither a variable nor a valid entity scope:
>   `type_error(scope, Scope)`

#### Examples

>     | ?- instantiates_class(water_jug, state_space).

>     | ?- instantiates_class(Space, state_space, public).

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