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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 get_metric(self, pronac, metric):
 """ Get metric for the project with the given pronac number. Usage: """


        assert isinstance(metric, str)
        assert '.' in metric, 'metric must declare a namespace'

        try:
            func = self._metrics[metric]
            return func(pronac, self._data)
        except KeyError:
            raise InvalidMetricError('metric does not exist')