Datafile is an Octue type that corresponds to a file, which may exist on your computer or in a cloud store. It has
the following main attributes:
path- the path of this file, which may include folders or subfolders, within the dataset.
cluster- the integer cluster of files, within a dataset, to which this belongs (default 0)
sequence- a sequence number of this file within its cluster (if sequences are appropriate)
tags- a space-separated string or iterable of tags relevant to this file
posix_timestamp- a posix timestamp associated with the file, in seconds since epoch, typically when it was created but could relate to a relevant time point for the data