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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 relation_get(attribute=None, unit=None, rid=None):
 """Get relation information"""

    _args = ['relation-get', '--format=json']
    if rid:
        _args.append('-r')
        _args.append(rid)
    _args.append(attribute or '-')
    if unit:
        _args.append(unit)
    try:
        return json.loads(subprocess.check_output(_args).decode('UTF-8'))
    except ValueError:
        return None
    except CalledProcessError as e:
        if e.returncode == 2:
            return None
        raise