return docker_image instead of return docker id
return docker_image instead of return docker id

StanfordBioinformatics/xppf,StanfordBioinformatics/loom,StanfordBioinformatics/xppf,StanfordBioinformatics/loom,StanfordBioinformatics/loom,StanfordBioinformatics/xppf,StanfordBioinformatics/loom,StanfordBioinformatics/xppf