remove duplicates from a list

def remove_duplicates(my_list):
    new_list = []
    for item in my_list:
        if item not in new_list:
            new_list.append(item)
    return new_list

remove_duplicates([1, 2, 2, 3, 4, 4, 5, 6, 6, 7, 8, 9])