code: def apply(self, s, active=None):
          
          if active is None:
              active = self.active
          return self.group.apply(s, active=active)
docs: Apply the REPP's rewrite rules to the input string *s*.
  
          Args:
              s (str): the input string to process
              active (optional): a collection of external module names
                  that may be applied if called
          Returns:
              a :class:`REPPResult` object containing the processed
                  string and characterization maps