'get existing info'

def get_existing(self):

    if self.config:
        if self.rate_limit:
            self.existing['rate_limit'] = get_rate_limit(self.config)
        if self.forward_enp_slot:
            self.existing['forward_enp_slot'] = get_forward_enp(self.config)
    if (not self.sflow_dict):
        return
    if self.agent_ip:
        self.existing['agent'] = self.sflow_dict['agent']
    if self.source_ip:
        self.existing['source'] = self.sflow_dict['source']
    if self.collector_id:
        self.existing['collector'] = self.sflow_dict['collector']
    if self.export_route:
        self.existing['export'] = self.sflow_dict['export']
    if self.sflow_interface:
        self.existing['sampling'] = self.sflow_dict['sampling']
        self.existing['counter'] = self.sflow_dict['counter']
