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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 list_():
    '''
    Returns the machine's bridges list

    CLI Example:

    .. code-block:: bash

        salt '*' bridge.list
    '''
    brs = _os_dispatch('brshow')
    if not brs:
        return None
    brlist = []
    for br in brs:
        brlist.append(br)

    return brlist