def uuid_adapter(obj, request):
    """Format the fields.UUID to return String

    ::

        from pyramid.renderers import JSON
        from uuid import UUID
        json_renderer = JSON()
        json_renderer.add_adapter(UUID, uuid_adapter)
        config.add_renderer('json', json_renderer)


    :param obj: uuid obj
    :rtype: str
    """
    return str(obj.hex)
