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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_ruby(ruby, runas=None):
    '''
    Uninstall a ruby implementation.

    ruby
        The version of ruby to uninstall. Should match one of the versions
        listed by :py:func:`rbenv.versions <salt.modules.rbenv.versions>`.

    runas
        The user under which to run rbenv. If not specified, then rbenv will be
        run as the user under which Salt is running.

    CLI Example:

    .. code-block:: bash

        salt '*' rbenv.uninstall_ruby 2.0.0-p0
    '''
    ruby = re.sub(r'^ruby-', '', ruby)
    _rbenv_exec(['uninstall', '--force', ruby], runas=runas)
    return True