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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 _selftoken_expired():
    '''
    Validate the current token exists and is still valid
    '''
    try:
        verify = __opts__['vault'].get('verify', None)
        url = '{0}/v1/auth/token/lookup-self'.format(__opts__['vault']['url'])
        if 'token' not in __opts__['vault']['auth']:
            return True
        headers = {'X-Vault-Token': __opts__['vault']['auth']['token']}
        response = requests.get(url, headers=headers, verify=verify)
        if response.status_code != 200:
            return True
        return False
    except Exception as e:
        raise salt.exceptions.CommandExecutionError(
            'Error while looking up self token : {0}'.format(six.text_type(e))
            )