code: def from_config(config, **options):
          
          expected_args = ('prefix', 'realclass')
          for arg in expected_args:
              if arg not in options:
                  msg = "Required option missing: {0}"
                  raise rconfig.ConfigurationError(msg.format(arg))
          # Not logging unrecognized options here, because they might be used
          # by the real event store instantiated below.
  
          classpath = options['realclass']
          classpath_pieces = classpath.split('.')
          classname = classpath_pieces[-1]
          modulepath = '.'.join(classpath_pieces[0:-1])
          module = importlib.import_module(modulepath)
          estore_class = getattr(module, classname)
  
          return RotatedEventStore(lambda fname: estore_class(fname),
                                   options['path'], options['prefix'])
docs: Instantiate an `RotatedEventStore` from config.
  
          Parameters:
          _config    -- the configuration file options read from file(s).
          **options -- various options given to the specific event store. Shall
                       not be used with this event store. Warning will be logged
                       for every extra non-recognized option. The only required
                       key to this function is 'path'.
  
          returns   -- a newly instantiated `RotatedEventStore`.