     }
     
     /**
-     Returns true if there are any keys registered with the given type in any container, independent of name.
+     Returns true if there are any keys registered with the given type and matching the metafilter query in any container, independent of name.
     */
     public static func exists<T, M>(type: T.Type, metafilter: @escaping Metafilter<M>) -> Bool {
         return exists(type: String(reflecting: type), name: nil, container: nil, metafilter: metathunk(metafilter))

 The type of a metadata filter.
 */
public typealias Metafilter<M> = (M) -> Bool

/**
 This class creates and holds a type-erasing thunk over a registration block.

        return exists(type: String(reflecting: type), name: nil, container: nil, metafilter: nil)
    }
    
    /**
     Returns true if any registrations exist matching the given metafilter, regardless of type, name, or container.
    */
    public static func exists<M>(metafilter: @escaping Metafilter<M>) -> Bool {
        return exists(type: nil, name: nil, container: nil, metafilter: metathunk(metafilter))
    }
