How to use the pygraphviz.agraph.Edge function in pygraphviz

def neighbors_iter(self, n):
        """Return iterator over the nodes attached to n.

        Note: modifying the graph structure while iterating over
        node neighbors may produce unpredictable results.  Use neighbors()
        as an alternative.
        """
        n = Node(self, n)
        nh = n.handle
        eh = gv.agfstedge(self.handle, nh)
        while eh is not None:
            (s, t) = Edge(self, eh=eh)
            if s == n:
                yield Node(self, t)
            else:
                yield Node(self, s)
            try:
                eh = gv.agnxtedge(self.handle, eh, nh)
            except StopIteration:
                return

def has_edge(self, u, v=None, key=None):
        """Return True an edge u-v is in the graph or False if not.

        >>> G=AGraph()
        >>> G.add_edge('a','b')
        >>> G.has_edge('a','b')
        True

        Optional key argument will restrict match to edges (u,v,key).

        """

        if v is None:
            (u,v)=u  # no v given, assume u is an edge tuple
        try:
            Edge(self,u,v,key)
            return True
        except KeyError:
            return False

while nh is not None:
                eh=gv.agfstout(self.handle,nh)
                while eh is not None:
                    e=Edge(self,eh=eh)
                    if keys:
                        yield (e[0],e[1],e.name)
                    else:
                        yield e
                    eh=gv.agnxtout(self.handle,eh)
                nh=gv.agnxtnode(self.handle,nh)
        elif nbunch in self: # if nbunch is a single node
            n=Node(self,nbunch)
            nh=n.handle
            eh=gv.agfstout(self.handle,nh)
            while eh is not None:
                e=Edge(self,eh=eh)
                if keys:
                    yield (e[0],e[1],e.name)
                else:
                    yield e
                eh=gv.agnxtout(self.handle,eh)
        else:                # if nbunch is a sequence of nodes
            try: bunch=[n for n in nbunch if n in self]
            except TypeError:
                raise TypeError("nbunch is not a node or a sequence of nodes.")
            for n in nbunch:
                try:
                    nh=Node(self,n).handle
                except KeyError:
                    continue
                eh=gv.agfstout(self.handle,nh)
                while eh is not None:

try:
            vh = Node(self, v).handle
        except:
            self.add_node(v)
            vh = Node(self, v).handle
        if key is not None:
            if not is_string_like(key):
                key = str(key)
            key = key.encode(self.encoding)
        try:
            # new
            eh = gv.agedge(self.handle, uh, vh, key, _Action.create)
        except KeyError:
            # for strict graph, or already added
            eh = gv.agedge(self.handle, uh, vh, key, _Action.find)
        e = Edge(self, eh=eh)
        e.attr.update(**attr)

eh = gv.agnxtout(self.handle, eh)
                except StopIteration:
                    return
        else:                # if nbunch is a sequence of nodes
            try:
                bunch = [n for n in nbunch if n in self]
            except TypeError:
                raise TypeError("nbunch is not a node or a sequence of nodes.")
            for n in nbunch:
                try:
                    nh = Node(self, n).handle
                except KeyError:
                    continue
                eh = gv.agfstout(self.handle, nh)
                while eh is not None:
                    e = Edge(self, eh=eh)
                    if keys:
                        yield (e[0], e[1], e.name)
                    else:
                        yield e
                    try:
                        eh = gv.agnxtout(self.handle, eh)
                    except StopIteration:
                        break

except TypeError:
            raise TypeError("Subgraph name must be a string: %s" % name.decode(self.encoding))

        H = self.__class__(strict=self.strict,
                           directed=self.directed,
                           handle=handle, name=name,
                           **attr)
        if nbunch is None: return H
        # add induced subgraph on nodes in nbunch
        bunch = self.prepare_nbunch(nbunch)
        for n in bunch:
            node = Node(self, n)
            nh = gv.agsubnode(handle, node.handle, _Action.create)
        for (u, v, k) in self.edges(keys=True):
            if u in H and v in H:
                edge = Edge(self, u, v, k)
                eh = gv.agsubedge(handle, edge.handle, _Action.create)

        return H

def remove_edge(self, u, v=None, key=None):
        """Remove edge between nodes u and v from the graph.

        With optional key argument will only remove an edge
        matching (u,v,key).

        """
        if v is None:
            (u, v) = u  # no v given, assume u is an edge tuple
        e = Edge(self, u, v, key)
        try:
            gv.agdeledge(self.handle, e.handle)
        except KeyError:
            raise KeyError("Edge %s-%s not in graph." % (u, v))

def in_edges_iter(self, nbunch=None, keys=False):
        """Return iterator over out edges in the graph.

        If the optional nbunch (container of nodes) only out edges
        adjacent to nodes in nbunch will be returned.

        Note: modifying the graph structure while iterating over
        edges may produce unpredictable results.  Use in_edges()
        as an alternative.
        """
        if nbunch is None:   # all nodes
            nh=gv.agfstnode(self.handle)
            while nh is not None:
                eh=gv.agfstin(self.handle,nh)
                while eh is not None:
                    e=Edge(self,eh=eh)
                    if keys:
                        yield (e[0],e[1],e.name)
                    else:
                        yield e
                    eh=gv.agnxtin(self.handle,eh)
                nh=gv.agnxtnode(self.handle,nh)
        elif nbunch in self: # if nbunch is a single node
            n=Node(self,nbunch)
            nh=n.handle
            eh=gv.agfstin(self.handle,nh)
            while eh is not None:
                e=Edge(self,eh=eh)
                if keys:
                    yield (e[0],e[1],e.name)
                else:
                    yield e

def in_edges_iter(self, nbunch=None, keys=False):
        """Return iterator over out edges in the graph.

        If the optional nbunch (container of nodes) only out edges
        adjacent to nodes in nbunch will be returned.

        Note: modifying the graph structure while iterating over
        edges may produce unpredictable results.  Use in_edges()
        as an alternative.
        """
        if nbunch is None:   # all nodes
            nh = gv.agfstnode(self.handle)
            while nh is not None:
                eh = gv.agfstin(self.handle, nh)
                while eh is not None:
                    e = Edge(self, eh=eh)
                    if keys:
                        yield (e[0], e[1], e.name)
                    else:
                        yield e
                    try:
                        eh = gv.agnxtin(self.handle, eh)
                    except StopIteration:
                        break
                try:
                    nh = gv.agnxtnode(self.handle, nh)
                except StopIteration:
                    return
        elif nbunch in self: # if nbunch is a single node
            n = Node(self, nbunch)
            nh = n.handle
            eh = gv.agfstin(self.handle, nh)