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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 clear(self):
 """Clear all nodes from this sensor_graph. This function is equivalent to just creating a new SensorGraph() object from scratch. It does not clear any data from the SensorLog, however. """


        self.roots = []
        self.nodes = []
        self.streamers = []

        self.constant_database = {}
        self.metadata_database = {}
        self.config_database = {}