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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):
 """Creates outputs. Outputs are files made by a backend."""

        if os.path.exists(self.build_path) and not os.path.isdir(self.build_path):
            self._logger.error('Output path must be a folder if it already exists')
            return
        Compiler._mkdir(self.build_path)
        self._execute_backend_on_spec()