I cant add a contact with gst_no getting error {"code":8,"message":"Invalid Element gst_no"}

I cant add a contact with gst_no getting error {"code":8,"message":"Invalid Element gst_no"}

am trying to add a contact into zoho books but when i add the key "gst_no" into the post data am getting error {"code":8,"message":"Invalid Element gst_no"} ,but if i remove the key contact will be added, am adding my postdata for reference to see if am missing something
body_data = {
"contact_name": "test",
"company_name": "test",
"billing_address": {
"attention": "sheffin",
"address": "4900 Hopyard Rd",
"city": "ernakulam",
"state": "kerala",
"zip": 692021,
"country": "IN",
"phone": "+91123456789"
},
"shipping_address": {
"attention": "sheffin",
"address": "4900 Hopyard Rd",
"city": "Pleasanton",
"state": "kerala",
"zip": 94588,
"country": "IN",
"phone": "+91123456789"
},
"gst_no":"22AAAAA0000A1Z5",
"first_name":"sheffin",
"last_name":"Sheffin",
"email":"test@gmail.com",
"mobile":"+91123456789",
}

thank you for your help is advance