Is your feature request related to a problem? Please describe.
the current data list utility assumes that when the key is "test", the data is a list of filenames.

would be great to optionally support the testing data in the form of a list of dictionaries, to be consistent with the 'training' list, for example,

        "test":
        [
            {'image': '/workspace/data/chest_19.nii.gz',  'othermetafield': 0},
            {'image': '/workspace/data/chest_31.nii.gz',  'othermetafield': 1}
        ]