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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def getitem(source, index):
 """Forward one or several items from an asynchronous sequence. The argument can either be a slice or an integer. See the slice and item operators for more information. """

    if isinstance(index, builtins.slice):
        return slice.raw(source, index.start, index.stop, index.step)
    if isinstance(index, int):
        return item.raw(source, index)
    raise TypeError("Not a valid index (int or slice)")