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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 uninstall(gems, ruby=None, runas=None, gem_bin=None):
    '''
    Uninstall one or several gems.

    :param gems: string
        The gems to uninstall.
    :param gem_bin: string : None
        Full path to ``gem`` binary to use.
    :param ruby: string : None
        If RVM or rbenv are installed, the ruby version and gemset to use.
        Ignored if ``gem_bin`` is specified.
    :param runas: string : None
        The user to run gem as.

    CLI Example:

    .. code-block:: bash

        salt '*' gem.uninstall vagrant
    '''
    try:
        gems = gems.split()
    except AttributeError:
        pass

    return _gem(['uninstall'] + gems + ['-a', '-x'],
                ruby,
                gem_bin=gem_bin,
                runas=runas)