'Return a directed copy of the graph.
Returns
G : MultiDiGraph
A deepcopy of the graph.
Notes
If edges in both directions (u, v) and (v, u) exist in the
graph, attributes for the new undirected edge will be a combination of
the attributes of the directed edges.  The edge data is updated
in the (arbitrary) order that the edges are encountered.  For
more customized control of the edge attributes use add_edge().
This returns a "deepcopy" of the edge, node, and
graph attributes which attempts to completely copy
all of the data and references.
This is in contrast to the similar G=DiGraph(D) which returns a
shallow copy of the data.
See the Python copy module for more information on shallow
and deep copies, http://docs.python.org/library/copy.html.
Examples
>>> G = nx.Graph()   # or MultiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges())
[(0, 1), (1, 0)]
If already directed, return a (deep) copy
>>> G = nx.MultiDiGraph()
>>> key = G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges())
[(0, 1)]'

def to_directed(self):

    return deepcopy(self)
