Returns a ``Collection`` **class** for a given service.

        :param service_name: A string that specifies the name of the desired
            service. Ex. ``sqs``, ``sns``, ``dynamodb``, etc.
        :type service_name: string

        :param collection_name: A string that specifies the name of the desired
            class. Ex. ``QueueCollection``, ``NotificationCollection``,
            ``TableCollection``, etc.
        :type collection_name: string

        :param base_class: (Optional) The base class of the object. Prevents
            "magically" loading the wrong class (one with a different base).
        :type base_class: class

        :rtype: <kotocore.collections.Collection subclass>

def get_collection(self, service_name, collection_name, base_class=None):
        """
        Returns a ``Collection`` **class** for a given service.

        :param service_name: A string that specifies the name of the desired
            service. Ex. ``sqs``, ``sns``, ``dynamodb``, etc.
        :type service_name: string

        :param collection_name: A string that specifies the name of the desired
            class. Ex. ``QueueCollection``, ``NotificationCollection``,
            ``TableCollection``, etc.
        :type collection_name: string

        :param base_class: (Optional) The base class of the object. Prevents
            "magically" loading the wrong class (one with a different base).
        :type base_class: class

        :rtype: <kotocore.collections.Collection subclass>
        """
        try:
            return self.cache.get_collection(
                service_name,
                collection_name,
                base_class=base_class
            )
        except NotCached:
            pass

        # We didn't find it. Construct it.
        new_class = self.collection_factory.construct_for(
            service_name,
            collection_name,
            base_class=base_class
        )
        self.cache.set_collection(service_name, collection_name, new_class)
        return new_class