'Judge whether proposed vpn target has existed'

def judge_if_vpn_target_exist(self, vpn_target_type):

    vpn_target = list()
    if (vpn_target_type == 'vpn_target_import'):
        vpn_target.extend(self.existing['vpn_target_both'])
        vpn_target.extend(self.existing['vpn_target_import'])
        return set(self.proposed['vpn_target_import']).issubset(vpn_target)
    elif (vpn_target_type == 'vpn_target_export'):
        vpn_target.extend(self.existing['vpn_target_both'])
        vpn_target.extend(self.existing['vpn_target_export'])
        return set(self.proposed['vpn_target_export']).issubset(vpn_target)
    return False
