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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 build(self, root="runs"):
 """ Build a nested directory structure, starting in ``root`` :param root: Root directory for structure """


        for d, control in self.iter(root):
            _mkdirs(d)
            with open(os.path.join(d, self.control_name), 'w') as fp:
                json.dump(control, fp, indent=self.indent)
                # RJSON and some other tools like a trailing newline
                fp.write('\n')