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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 create_loopback(file_path):
    '''
    Create a loopback device for a given backing file.

    :returns: str: Full path to new loopback device (eg, /dev/loop0)
    '''
    file_path = os.path.abspath(file_path)
    check_call(['losetup', '--find', file_path])
    for d, f in six.iteritems(loopback_devices()):
        if f == file_path:
            return d