<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def index(self, item):
 """ Not recommended for use on large lists due to time complexity, but it works -> #int list index of @item """

        for i, x in enumerate(self.iter()):
            if x == item:
                return i
        return None