def file_size(file_ref, config=None):
    """Retrieve file size in keep, in Mb
    """
    import arvados
    api_client = _get_api_client(config)
    coll_uuid, coll_ref = file_ref.replace("keep:", "").split("/", 1)
    cr = arvados.CollectionReader(coll_uuid, api_client=api_client)
    file = cr[coll_ref]
    return file.size() / (1024.0 * 1024.0)

# ## Fill in files from input collections
dataset/ETHPy150Open chapmanb/bcbio-nextgen-vm/bcbiovm/arvados/retriever.py/file_size/original