Makes a call on the Collection API

        :param collection_id: Id of the collection to retrieve
        :param nav: Direction of the navigation
        :param page: Page to retrieve
        :return: Response
        :rtype: requests.Response

def get_collection(self, collection_id=None, nav="children", page=None):
        """ Makes a call on the Collection API

        :param collection_id: Id of the collection to retrieve
        :param nav: Direction of the navigation
        :param page: Page to retrieve
        :return: Response
        :rtype: requests.Response
        """
        return self.call(
            "collections",
            {
                "id": collection_id,
                "nav": nav,
                "page": page
            },
            defaults={
                "id": None,
                "nav": "children",
                "page": 1
            }
        )