Convert a set of pending item updates into the structure
        required by Layer1.

def dynamize_attribute_updates(self, pending_updates):
        """
        Convert a set of pending item updates into the structure
        required by Layer1.
        """
        d = {}
        for attr_name in pending_updates:
            action, value = pending_updates[attr_name]
            if value is None:
                # DELETE without an attribute value
                d[attr_name] = {"Action": action}
            else:
                d[attr_name] = {"Action": action,
                                "Value": self.dynamize_value(value)}
        return d