code: def get_extension(self, publisher_name, extension_name, version=None, flags=None, account_token=None, account_token_header=None):
          
          route_values = {}
          if publisher_name is not None:
              route_values['publisherName'] = self._serialize.url('publisher_name', publisher_name, 'str')
          if extension_name is not None:
              route_values['extensionName'] = self._serialize.url('extension_name', extension_name, 'str')
          query_parameters = {}
          if version is not None:
              query_parameters['version'] = self._serialize.query('version', version, 'str')
          if flags is not None:
              query_parameters['flags'] = self._serialize.query('flags', flags, 'str')
          if account_token is not None:
              query_parameters['accountToken'] = self._serialize.query('account_token', account_token, 'str')
          response = self._send(http_method='GET',
                                location_id='e11ea35a-16fe-4b80-ab11-c4cab88a0966',
                                version='5.1-preview.2',
                                route_values=route_values,
                                query_parameters=query_parameters)
          return self._deserialize('PublishedExtension', response)
docs: GetExtension.
          [Preview API]
          :param str publisher_name:
          :param str extension_name:
          :param str version:
          :param str flags:
          :param str account_token:
          :param String account_token_header: Header to pass the account token
          :rtype: :class:`<PublishedExtension> <azure.devops.v5_1.gallery.models.PublishedExtension>`