ModuleNotFoundError: No module named 'frappe.model'

Question

import frappe

from frappe.model.document import Document

class ServersideScripting(Document):

        def validate(self):

                frappe.throw("hello")

when I try to run this script from serverside scripting it throws the following error:

import frappe

Traceback (most recent call last):

  File "/opt/bench/frappe-bench/apps/frappe/frappe/programming_module/doctype/serverside_scripting/serverside_scripting.py", line 5, in <module>

    from frappe.model.document import Document

ModuleNotFoundError: No module named 'frappe.model'

Where as the model exist in frappe at the following path /opt/bench/frappe-bench/apps/frappe/frappe

I tried changing the path in ~/.bashrc file still, import error occurs