<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def of(cls, part_class):
 """ Creates a new class with the ``item_class`` attribute properly set. """

        copy = type(
            "VectorOf%s" % part_class.__name__,
            cls.__bases__, dict(cls.__dict__)
        )
        copy.item_class = part_class

        return copy