'Return the platform label, or None if platform label is not set.'

def get_platform_label(self):

    if self.job:
        keyval_path = os.path.join(self.job.resultdir, 'host_keyvals', self.hostname)
        keyvals = utils.read_keyval(keyval_path)
        return keyvals.get('platform', None)
    else:
        return None
