docs: def update_soa_serial(server, token, soa_content):
      """Update SOA serial
  
      Argument:
  
          server:      TonicDNS API server
          token:       TonicDNS API authentication token
          soa_content: SOA record data
  
      x-authentication-token: token
      Get SOA record
      `cur_soa` is current SOA record.
      `new_soa` is incremental serial SOA record.
      """
      method = 'GET'
      uri = 'https://' + server + '/zone/' + soa_content.get('domain')
      cur_soa, new_soa = connect.tonicdns_client(
          uri, method, token, data=False, keyword='serial', content=soa_content)
      # set JSON
  
      domain = soa_content.get('domain')
      cur_o = JSONConverter(domain)
      new_o = JSONConverter(domain)
      cur_o.records = [cur_soa]
      new_o.records = [new_soa]
      cur_o.generata_data(False)
      new_o.generata_data(True)
  
      # Create new SOA record
      uri = 'https://' + server + '/zone/' + domain
      method = 'PUT'
      connect.tonicdns_client(uri, method, token, new_o.dict_records[0])
  
      # Delete current SOA record why zone has only one SOA record.
      method = 'DELETE'
      uri = 'https://' + server + '/zone'
      connect.tonicdns_client(uri, method, token, cur_o.dict_records[0])