'Encode settings for the field description
@param field: a Field instance
@return: a dict with the field settings'

@classmethod
def settings(cls, field):

    settings = {}
    if (not field.readable):
        settings['readable'] = False
    if (not field.writable):
        settings['writable'] = False
    if cls.is_required(field):
        settings['required'] = True
    return settings
