'Return a directed copy of the graph.
Returns
G : DiGraph
A deepcopy of the graph.
Notes
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 D=DiGraph(G) 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.DiGraph()   # or MultiDiGraph, etc
>>> G.add_edge(0, 1)
>>> H = G.to_directed()
>>> list(H.edges())
[(0, 1)]'

def to_directed(self):

    return deepcopy(self)
