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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 _add_single_metric(self, timestamp, metric_name, value):
 """Store a single metric in the _data dict which can be converted to a dataframe. """

        # note that this method is built this way to make it possible to
        # support live-refreshing charts in Bokeh at some point in the future.
        self._data['timestamp'].append(timestamp)
        self._data['metric_name'].append(metric_name)
        self._data['value'].append(value)