code: def determine_reach_subtype(event_name):
      
  
      best_match_length = None
      best_match = None
      for ss in reach_rule_regexps:
          if re.search(ss, event_name):
              if best_match is None or len(ss) > best_match_length:
                  best_match = ss
                  best_match_length = len(ss)
  
      return best_match
docs: Returns the category of reach rule from the reach rule instance.
  
      Looks at a list of regular
      expressions corresponding to reach rule types, and returns the longest
      regexp that matches, or None if none of them match.
  
      Parameters
      ----------
      evidence : indra.statements.Evidence
          A reach evidence object to subtype
  
      Returns
      -------
      best_match : str
          A regular expression corresponding to the reach rule that was used to
          extract this evidence