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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 storage_list(storage_name=None):
 """List the storage IDs for the unit"""

    _args = ['storage-list', '--format=json']
    if storage_name:
        _args.append(storage_name)
    try:
        return json.loads(subprocess.check_output(_args).decode('UTF-8'))
    except ValueError:
        return None
    except OSError as e:
        import errno
        if e.errno == errno.ENOENT:
            # storage-list does not exist
            return []
        raise