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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 fetchMore(self, parentIndex):
 # TODO: Make LazyLoadRepoTreeModel? """ Fetches any available data for the items with the parent specified by the parent index. """

        parentItem = self.getItem(parentIndex)
        if not parentItem:
            return

        if not parentItem.canFetchChildren():
            return

        # TODO: implement InsertItems to optimize?
        for childItem in parentItem.fetchChildren():
            self.insertItem(childItem, parentIndex=parentIndex)

        # Check that Rti implementation correctly sets canFetchChildren
        assert not parentItem.canFetchChildren(), \
            "not all children fetched: {}".format(parentItem)