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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 bridge_exists(br):
    '''
    Tests whether bridge exists as a real or fake  bridge.

    Returns:
        True if Bridge exists, else False.

    .. versionadded:: 2016.3.0

    CLI Example:
    .. code-block:: bash

        salt '*' openvswitch.bridge_exists br0
    '''
    cmd = 'ovs-vsctl br-exists {0}'.format(br)
    result = __salt__['cmd.run_all'](cmd)
    retcode = result['retcode']
    return _retcode_to_bool(retcode)