Is there any way to exclude data.scene variables from the undo stack?

Question

I am registering a global variable and I need it to be ignored by UNDO and I need functionality like:

do some operators

get some information from the operations

add the information to the variable

undo to before the operators

keep the information in the variable

import bpy


class test_vars(bpy.types.PropertyGroup):
    val_1 = bpy.props.StringProperty(
        name = "val_1",
        description = "1",
        default = "")


class DoSomethingWithVal(bpy.types.Operator):
    bl_idname = "test.dosomethingwithval"
    bl_label = "test"
    bl_options = {'REGISTER', 'UNDO'}

    def execute(self, context):
        # do something
        pass

        return {'FINISHED'}


def register():
    bpy.utils.register_class(DoSomethingWithVal)
    bpy.utils.register_class(test_vars)
    bpy.types.Scene.do_something_vars = bpy.props.PointerProperty(type = test_vars)


def unregister():
    bpy.utils.unregister_class(DoSomethingWithVal)
    del bpy.types.Scene.do_something_vars


if __name__ == "__main__":
    register()

is it possible?