code: def grep(self, path, content, flags):
          
          try:
              match = re.compile(content, flags)
          except sre_constants.error as ex:
              print("Bad regexp: %s" % (ex))
              return
  
          for gpath, matches in self.do_grep(path, match):
              yield (gpath, matches)
docs: grep every child path under path for content