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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 fill(self, paths):
 """ Initialise the tree. paths is a list of strings where each string is the relative path to some file. """

        for path in paths:
            tree = self.tree
            parts = tuple(path.split('/'))
            dir_parts = parts[:-1]
            built = ()
            for part in dir_parts:
                self.cache[built] = tree
                built += (part, )
                parent = tree
                tree = parent.folders.get(part, empty)
                if tree is empty:
                    tree = parent.folders[part] = TreeItem(name=built, folders={}, files=set(), parent=parent)

            self.cache[dir_parts] = tree
            tree.files.add(parts[-1])