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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 versions(runas=None):
    '''
    List the installed versions of ruby

    CLI Example:

    .. code-block:: bash

        salt '*' rbenv.versions
    '''
    ret = _rbenv_exec(['versions', '--bare'], runas=runas)
    return [] if ret is False else ret.splitlines()