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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 _check_stems(files):
 """check if stem names are the same and use full path then"""

    used = set()
    for fn in files:
        if os.path.basename(fn) in used:
            logger.warning("%s stem is multiple times in your file list, "
                         "so we don't know "
                         "how to assign it to the sample data in the CSV. "
                         "We are gonna use full path to make a difference, "
                         "that means paired files should be in the same folder. "
                         "If this is a problem, you should rename the files you want "
                         "to merge. Sorry, no possible magic here." % os.path.basename(fn)
                         )
            return True
        used.add(os.path.basename(fn))
    return False