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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 revdep_rebuild(lib=None):
    '''
    Fix up broken reverse dependencies

    lib
        Search for reverse dependencies for a particular library rather
        than every library on the system. It can be a full path to a
        library or basic regular expression.

    CLI Example:

    .. code-block:: bash

        salt '*' gentoolkit.revdep_rebuild
    '''
    cmd = 'revdep-rebuild -i --quiet --no-progress'
    if lib is not None:
        cmd += ' --library={0}'.format(lib)
    return __salt__['cmd.retcode'](cmd, python_shell=False) == 0