This class method converts a generator of ``(K, V)`` tuples (the
        *tuple protocol*), where ``V`` is not yet of the correct type, to a
        generator where it is of the correct type (using the ``coerceitem``
        class property)

def coerce_tuples(cls, generator):
        """This class method converts a generator of ``(K, V)`` tuples (the
        *tuple protocol*), where ``V`` is not yet of the correct type, to a
        generator where it is of the correct type (using the ``coerceitem``
        class property)
        """
        for k, v in generator:
            yield k, cls.coerce_value(v)