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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 extend(self, other):
 """See list.extend."""

        index = len(self)
        length = 0
        for length, element in enumerate(other, 1):
            super(ObservableList, self).append(element)
        if length:
            self._notify_add_at(index, length)