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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_duration(self, matrix_name):
 """ Get duration for a concrete matrix. Args: matrix_name (str):
 name of the Matrix. Returns: float: duration of concrete matrix in seconds. """

        duration = 0.0
        if matrix_name in self.data:
            duration = sum([stage.duration() for stage in self.data[matrix_name]])
        return duration