GetDeploymentGroup.
        [Preview API] Get a deployment group by its ID.
        :param str project: Project ID or project name
        :param int deployment_group_id: ID of the deployment group.
        :param str action_filter: Get the deployment group only if this action can be performed on it.
        :param str expand: Include these additional details in the returned object.
        :rtype: :class:`<DeploymentGroup> <azure.devops.v5_0.task_agent.models.DeploymentGroup>`

def get_deployment_group(self, project, deployment_group_id, action_filter=None, expand=None):
        """GetDeploymentGroup.
        [Preview API] Get a deployment group by its ID.
        :param str project: Project ID or project name
        :param int deployment_group_id: ID of the deployment group.
        :param str action_filter: Get the deployment group only if this action can be performed on it.
        :param str expand: Include these additional details in the returned object.
        :rtype: :class:`<DeploymentGroup> <azure.devops.v5_0.task_agent.models.DeploymentGroup>`
        """
        route_values = {}
        if project is not None:
            route_values['project'] = self._serialize.url('project', project, 'str')
        if deployment_group_id is not None:
            route_values['deploymentGroupId'] = self._serialize.url('deployment_group_id', deployment_group_id, 'int')
        query_parameters = {}
        if action_filter is not None:
            query_parameters['actionFilter'] = self._serialize.query('action_filter', action_filter, 'str')
        if expand is not None:
            query_parameters['$expand'] = self._serialize.query('expand', expand, 'str')
        response = self._send(http_method='GET',
                              location_id='083c4d89-ab35-45af-aa11-7cf66895c53e',
                              version='5.0-preview.1',
                              route_values=route_values,
                              query_parameters=query_parameters)
        return self._deserialize('DeploymentGroup', response)