Error while send additional parameter to open_mapped_doc

While using frappe.model.open_mapped_doc() it just takes only object with two parameters :

			frappe.model.open_mapped_doc({
				method: ,
				frm: ,
			}) 

I am trying to add a third parameter but python always throw an error

missing 1 required positional

Here is my code in Java Script file

function fun(frm){
	let selected = frm.get_selected()
	frappe.model.open_mapped_doc({
		method: 'my_func_path_in_python_file',
		frm: frm,
		my_third_paramter: selected
	})
}

Here is my code in Python File

@frappe.whitelist()
def my_fun(source_name,my_third_paramter):
	def update_item(source, target, source_parent):
		target.field = selected_row

	doclist = get_mapped_doc("Customer",source_name, {
		"Customer": {
			"doctype": "Maintenance Work Order",
			"field_map": {
			}
		},"postprocess": update_item
	})
	return doclist

So Any Help Please !!!