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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_node(self, node, weight=None):
 """ Adds a single node to the Graph. Parameters node: str, int, or any hashable python object. The node to add to the graph. weight: int, float The weight of the node. Examples -------- ['A'] Adding a node with some weight. The weight of these nodes can be accessed as: {'weight': 0.3} {'weight': None} """


        # Check for networkx 2.0 syntax
        if isinstance(node, tuple) and len(node) == 2 and isinstance(node[1], dict):
            node, attrs = node
            if attrs.get('weight', None) is not None:
                attrs['weight'] = weight
        else:
            attrs = {'weight': weight}

        super(DAG, self).add_node(node, weight=weight)