'NoneType' object is not callable
Traceback (most recent call last):
python3.8/site-packages/knack/cli.py, ln 215, in invoke
    cmd_result = self.invocation.execute(args)
cli/core/commands/__init__.py, ln 654, in execute
    raise ex
cli/core/commands/__init__.py, ln 718, in _run_jobs_serially
    results.append(self._run_job(expanded_arg, cmd_copy))
cli/core/commands/__init__.py, ln 711, in _run_job
    six.reraise(*sys.exc_info())
...
cli/command_modules/vm/custom.py, ln 648, in assign_vm_identity
    assign_identity_helper(cmd.cli_ctx, getter, setter, identity_role=identity_role_id, identity_scope=identity_scope)
cli/core/commands/arm.py, ln 1057, in assign_identity
    resource = setter(resource)
cli/command_modules/vm/custom.py, ln 642, in setter
    vm.identity.user_assigned_identities[identity] = VirtualMachineIdentityUserAssignedIdentitiesValue()
TypeError: 'NoneType' object is not callable