How to pass the header application/json in Get method of swagger.json

Hey all 
i just want to integrate my flask rest api in swagger by using 

flask_swagger_ui 

I had already integrated few api but when i'm hitting the "Get" method api, i'm getting error "None type object"
i am passing the id as parameter but it is expecting the data in the form of json

Can anyone help me how to pass the headers i.e., application/json for Get method in swagger.json file