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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 read(string):
 """ Read a graph from a string in Dot language and return it. Nodes and edges specified in the input will be added to the current graph. @type string: string @param string: Input string in Dot format specifying a graph. @rtype: graph @return: Graph """

    
    dotG = pydot.graph_from_dot_data(string)
    
    if (dotG.get_type() == "graph"):
        G = graph()
    elif (dotG.get_type() == "digraph"):
        G = digraph()
    elif (dotG.get_type() == "hypergraph"):
        return read_hypergraph(string)
    else:
        raise InvalidGraphType
    
    # Read nodes...
    # Note: If the nodes aren't explicitly listed, they need to be
    for each_node in dotG.get_nodes():
        G.add_node(each_node.get_name())
        for each_attr_key, each_attr_val in each_node.get_attributes().items():
            G.add_node_attribute(each_node.get_name(), (each_attr_key, each_attr_val))
    
    # Read edges...
    for each_edge in dotG.get_edges():
        # Check if the nodes have been added
        if not G.has_node(each_edge.get_source()):
            G.add_node(each_edge.get_source())
        if not G.has_node(each_edge.get_destination()):
            G.add_node(each_edge.get_destination())
        
        # See if there's a weight
        if 'weight' in each_edge.get_attributes().keys():
            _wt = each_edge.get_attributes()['weight']
        else:
            _wt = 1
        
        # See if there is a label
        if 'label' in each_edge.get_attributes().keys():
            _label = each_edge.get_attributes()['label']
        else:
            _label = ''
        
        G.add_edge((each_edge.get_source(), each_edge.get_destination()), wt = _wt, label = _label)
        
        for each_attr_key, each_attr_val in each_edge.get_attributes().items():
            if not each_attr_key in ['weight', 'label']:
                G.add_edge_attribute((each_edge.get_source(), each_edge.get_destination()), \
                                            (each_attr_key, each_attr_val))
    
    return G