code: def get_config(self, key, default=MISSING):
          
  
          keyname = "config:" + key
  
          try:
              return self.kvstore.get(keyname)
          except KeyError:
              if default is MISSING:
                  raise ArgumentError("No config value found for key", key=key)
  
              return default
docs: Get the value of a persistent config key from the registry
  
          If no default is specified and the key is not found ArgumentError is raised.
  
          Args:
              key (string): The key name to fetch
              default (string): an optional value to be returned if key cannot be found
  
          Returns:
              string: the key's value