Write a function that avoids mutable default args

Summary

Learn how to write functions that use immutable defaults to avoid shared mutable state between calls.

Problem statement

In Python, using a mutable object (like a list) as a default argument is a common pitfall because the same object is reused across calls. Your task is to implement append_to(element, lst=None) that appends element to lst and returns the list. If lst is not provided (None), create and use a new list for that call so calls don't share state.

Task

Implement a function that safely appends an element to a list without using a mutable default argument.

Examples

Input format

A function call append_to(element, lst=None). element may be any value; lst is optional.

Output format

Return the list after appending the element. The returned value will be shown as a Python list string representation.

Constraints

Do not use a mutable object as a default value. If lst is None, create a new list inside the function.

Samples