code: func (args Args) ExactMatch(key, source string) bool {
  	fieldValues, ok := args.fields[key]
  	//do not filter if there is no filter set or cannot determine filter
  	if !ok || len(fieldValues) == 0 {
  		return true
  	}
  
  	// try to match full name value to avoid O(N) regular expression matching
  	return fieldValues[source]
  }
docs: // ExactMatch returns true if the source matches exactly one of the values.