<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_robot_variables():
 """Return list of Robot Framework -compatible cli-variables parsed from ROBOT_-prefixed environment variable """

    prefix = 'ROBOT_'
    variables = []

    def safe_str(s):
        if isinstance(s, six.text_type):
            return s
        else:
            return six.text_type(s, 'utf-8', 'ignore')
    for key in os.environ:
        if key.startswith(prefix) and len(key) > len(prefix):
            variables.append(safe_str(
                '%s:%s' % (key[len(prefix):], os.environ[key]),
            ))
    return variables