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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def dimensions_from_subgroups(s):
 """ Given a sorted list of subgroups, return a string appropriate to provide as a composite track's `dimensions` arg. Parameters s : list of SubGroup objects (or anything with a `name` attribute) """

    letters = 'XYABCDEFGHIJKLMNOPQRSTUVWZ'
    return ' '.join(['dim{0}={1}'.format(dim, sg.name) for dim, sg in zip(letters, s)])