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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 flush(set=None, family='ipv4'):
    '''
    Flush entries in the specified set,
    Flush all sets if set is not specified.

    CLI Example:

    .. code-block:: bash

        salt '*' ipset.flush

        salt '*' ipset.flush set

        IPv6:
        salt '*' ipset.flush

        salt '*' ipset.flush set
    '''

    settype = _find_set_type(set)
    if not settype:
        return 'Error: Set {0} does not exist'.format(set)

    ipset_family = _IPSET_FAMILIES[family]
    if set:
        cmd = '{0} flush {1}'.format(_ipset_cmd(), set)
    else:
        cmd = '{0} flush'.format(_ipset_cmd())
    out = __salt__['cmd.run'](cmd, python_shell=False)

    return not out