Failing in API call

Hello Expert,
I wrote a API function in /home/vagrant/frappe-bench/apps/spms/spms/api.py

import frappe

@frappe.whitelist()
def ping():
    return 'pong'

Also created a user api-user and generated API Key and API Secret

use this in header Authorization: API Key:API Secret in postman.

But getting below error:

18:59:14 web.1            | Traceback (most recent call last):
18:59:14 web.1            |   File "apps/frappe/frappe/app.py", line 110, in application
18:59:14 web.1            |     response = frappe.api.handle(request)
18:59:14 web.1            |   File "apps/frappe/frappe/api/__init__.py", line 49, in handle
18:59:14 web.1            |     data = endpoint(**arguments)
18:59:14 web.1            |   File "apps/frappe/frappe/api/v1.py", line 36, in handle_rpc_call
18:59:14 web.1            |     return frappe.handler.handle()
18:59:14 web.1            |   File "apps/frappe/frappe/handler.py", line 49, in handle
18:59:14 web.1            |     data = execute_cmd(cmd)
18:59:14 web.1            |   File "apps/frappe/frappe/handler.py", line 82, in execute_cmd
18:59:14 web.1            |     is_whitelisted(method)
18:59:14 web.1            |   File "apps/frappe/frappe/__init__.py", line 821, in is_whitelisted
18:59:14 web.1            |     throw(msg, PermissionError, title="Method Not Allowed")
18:59:14 web.1            |   File "apps/frappe/frappe/__init__.py", line 565, in throw
18:59:14 web.1            |     msgprint(
18:59:14 web.1            |   File "apps/frappe/frappe/__init__.py", line 537, in msgprint
18:59:14 web.1            |     _raise_exception()
18:59:14 web.1            |   File "apps/frappe/frappe/__init__.py", line 488, in _raise_exception
18:59:14 web.1            |     raise exc
18:59:14 web.1            | frappe.exceptions.PermissionError: You are not permitted to access this resource.Function spms.api.ping is not whitelisted.

Seems user is not allowed to access the function. What role should I give to user api-user?

Please help.

Sorry my bad:
format should be:
token api_key:api_secret

I was excluding token keyword. Now it is working perfectly.