code: func (p *Project) Ps(ctx context.Context, services ...string) (InfoSet, error) {
  	allInfo := InfoSet{}
  
  	if len(services) == 0 {
  		services = p.ServiceConfigs.Keys()
  	}
  
  	for _, name := range services {
  
  		service, err := p.CreateService(name)
  		if err != nil {
  			return nil, err
  		}
  
  		info, err := service.Info(ctx)
  		if err != nil {
  			return nil, err
  		}
  
  		allInfo = append(allInfo, info...)
  	}
  	return allInfo, nil
  }
docs: // Ps list containers for the specified services.