code: func (args Args) MatchKVList(key string, sources map[string]string) bool {
  	fieldValues := args.fields[key]
  
  	//do not filter if there is no filter set or cannot determine filter
  	if len(fieldValues) == 0 {
  		return true
  	}
  
  	if len(sources) == 0 {
  		return false
  	}
  
  	for value := range fieldValues {
  		testKV := strings.SplitN(value, "=", 2)
  
  		v, ok := sources[testKV[0]]
  		if !ok {
  			return false
  		}
  		if len(testKV) == 2 && testKV[1] != v {
  			return false
  		}
  	}
  
  	return true
  }
docs: // MatchKVList returns true if all the pairs in sources exist as key=value
  // pairs in the mapping at key, or if there are no values at key.