<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_matching_rules(tweet):
 """ Retrieves the matching rules for a tweet with a gnip field enrichment. Args: tweet (Tweet):
 the tweet Returns: list: potential ``[{"tag": "user_tag", "value": "rule_value"}]`` pairs from standard rulesets or None if no rules or no matching_rules field is found. \n More information on this value at: http://support.gnip.com/enrichments/matching_rules.html """

    if is_original_format(tweet):
        rules = tweet.get("matching_rules")
    else:
        gnip = tweet.get("gnip")
        rules = gnip.get("matching_rules") if gnip else None
    return rules