How can we handle null values for Data type INTEGER while using Federated/External tables for Google Bigquery?

Question

While Using below query ,i am getting the error .

bq mk --use_legacy_sql=false --nullmarker="\N" --external_table_definition=/tmp/bqschema dataflowjson.TEST1 FATAL Flags parsing error: Unknown command line flag 'nullmarker' Run 'bq help' to get help

My Date is like :

Datatype that i am giving as : NAME:STRING,AGE:INTEGER,CITY:INTEGER