code: def load_extension(self, extension):
          
          # Load extension from installed pip package
          try:
              package = importlib.import_module(extension)
              extension_directory = package.__path__[0]
          except ImportError:
              message = linesep.join([traceback.format_exc(),
                                      'Error loading extension: `{}` is neither a directory, nor a package.'.format(extension),
                                      'Are you sure it is installed in your environment? If so, look at the stack trace above to determine the origin of this error.',
                                      'See more at <https://github.com/openfisca/openfisca-extension-template#installing>.'])
              raise ValueError(message)
  
          self.add_variables_from_directory(extension_directory)
          param_dir = path.join(extension_directory, 'parameters')
          if path.isdir(param_dir):
              extension_parameters = ParameterNode(directory_path = param_dir)
              self.parameters.merge(extension_parameters)
docs: Loads an extension to the tax and benefit system.
  
          :param string extension: The extension to load. Can be an absolute path pointing to an extension directory, or the name of an OpenFisca extension installed as a pip package.