Delete the sub-resource

        NOTE: Currently assumes subresources are stored within a dictionary,
        keyed with the subresource's ID

def delete_subresource(self, subresource):
        """
        Delete the sub-resource

        NOTE: Currently assumes subresources are stored within a dictionary,
        keyed with the subresource's ID
        """
        subresources = getattr(self, subresource.parent_key, {})
        del subresources[subresource.id]
        yield self._save()