How to use the pydot.pydot.Graph function in pydot

def __init__(self, *argsl, **argsd):
        Graph.__init__(self, *argsl, **argsd)

        self.shape_files = list()

        self.progs = None

        self.formats = ['canon', 'cmap', 'cmapx', 'cmapx_np', 'dia', 'dot',
            'fig', 'gd', 'gd2', 'gif', 'hpgl', 'imap', 'imap_np', 'ismap',
            'jpe', 'jpeg', 'jpg', 'mif', 'mp', 'pcl', 'pdf', 'pic', 'plain',
            'plain-ext', 'png', 'ps', 'ps2', 'svg', 'svgz', 'vml', 'vmlz',
            'vrml', 'vtx', 'wbmp', 'xdot', 'xlib' ]

        self.prog = 'dot'

        # Automatically creates all the methods enabling the creation
        # of output in any of the supported formats.
        for frmt in self.formats:

#
    def __init__(self, graph_name='', obj_dict=None, suppress_disconnected=False,
        simplify=False, **attrs):


        Graph.__init__(self, graph_name=graph_name, obj_dict=obj_dict,
            suppress_disconnected=suppress_disconnected, simplify=simplify, **attrs)

        if obj_dict is None:

            self.obj_dict['type'] = 'subgraph'




class Cluster(Graph):

    """Class representing a cluster in Graphviz's dot language.

    This class implements the methods to work on a representation
    of a cluster in Graphviz's dot language.

    cluster(graph_name='subG', suppress_disconnected=False, attribute=value, ...)

    graph_name:
        the cluster's name (the string 'cluster' will be always prepended)
    suppress_disconnected:
        defaults to false, which will remove from the
        cluster any disconnected nodes.
    All the attributes defined in the Graphviz dot language should
    be supported.

Graph.__init__(self, graph_name=graph_name, obj_dict=obj_dict,
            suppress_disconnected=suppress_disconnected, simplify=simplify, **attrs)

        if obj_dict is None:

            self.obj_dict['type'] = 'subgraph'
            self.obj_dict['name'] = 'cluster_'+graph_name

        self.create_attribute_methods(CLUSTER_ATTRIBUTES)






class Dot(Graph):
    """A container for handling a dot language file.

    This class implements methods to write and process
    a dot language file. It is a derived class of
    the base class 'Graph'.
    """



    def __init__(self, *argsl, **argsd):
        Graph.__init__(self, *argsl, **argsd)

        self.shape_files = list()

        self.progs = None

def set_parent_graph(self, parent_graph):

        self.obj_dict['parent_graph'] = parent_graph

        for obj_list in self.obj_dict['nodes'].itervalues():
            for obj in obj_list:
                obj['parent_graph'] = parent_graph

        for obj_list in self.obj_dict['edges'].itervalues():
            for obj in obj_list:
                obj['parent_graph'] = parent_graph

        for obj_list in self.obj_dict['subgraphs'].itervalues():
            for obj in obj_list:
                Graph(obj_dict=obj).set_parent_graph(parent_graph)

graph.append( edge.to_string() + '\n' )
                edges_done.add(edge)

            else:

                sgraph = Subgraph(obj_dict=obj)

                graph.append( sgraph.to_string()+'\n' )

        graph.append( '}\n' )

        return ''.join(graph)



class Subgraph(Graph):

    """Class representing a subgraph in Graphviz's dot language.

    This class implements the methods to work on a representation
    of a subgraph in Graphviz's dot language.

    subgraph(graph_name='subG', suppress_disconnected=False, attribute=value, ...)

    graph_name:
        the subgraph's name
    suppress_disconnected:
        defaults to false, which will remove from the
        subgraph any disconnected nodes.
    All the attributes defined in the Graphviz dot language should
    be supported.