GetVariableGroup.
        [Preview API] Get a variable group.
        :param str project: Project ID or project name
        :param int group_id: Id of the variable group.
        :rtype: :class:`<VariableGroup> <azure.devops.v5_1.task-agent.models.VariableGroup>`

def get_variable_group(self, project, group_id):
        """GetVariableGroup.
        [Preview API] Get a variable group.
        :param str project: Project ID or project name
        :param int group_id: Id of the variable group.
        :rtype: :class:`<VariableGroup> <azure.devops.v5_1.task-agent.models.VariableGroup>`
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if group_id is not None:
            route_values['groupId'] = self._serialize.url('group_id', group_id, 'int')
        response = self._send(http_method='GET',
                              location_id='f5b09dd5-9d54-45a1-8b5a-1c8287d634cc',
                              version='5.1-preview.1',
                              route_values=route_values)
        return self._deserialize('VariableGroup', response)