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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 _write_scalar(self, name:str, scalar_value, iteration:int)->None:
        "Writes single scalar value to Tensorboard."
        tag = self.metrics_root + name
        self.tbwriter.add_scalar(tag=tag, scalar_value=scalar_value, global_step=iteration)