[BUG] orient_graph removes some of the edges

[chhajer-rajul]

Describe the bug
While applying Orient graph to orient a CPDAG, the procedure removes some of the edges present in the graph. I specifically used ANM object to call this procedure.

def orient_graph(self, df_data, graph, printout=None, **kwargs):
       
        if isinstance(graph, nx.DiGraph):
            edges = [a for a in list(graph.edges()) if (a[1], a[0]) in list(graph.edges())]
            oriented_edges = [a for a in list(graph.edges()) if (a[1], a[0]) not in list(graph.edges())]

       Output of edges variable: 

[('V2', 'V7'),
('V3', 'V7'),
('V7', 'V2'),
('V7', 'V3'),
('V7', 'V8'),
('V8', 'V7'),
('V8', 'V9'),
('V9', 'V8')]

// below code deletes the edges from the edge list which later would be used for orientation

            for a in edges:
                if (a[1], a[0]) in list(graph.edges()):
                    edges.remove(a)
            output = nx.DiGraph()
            for i in oriented_edges:
                output.add_edge(*i)

       Output of edges variable: 

[('V7', 'V3'),
('V9', 'V8')]

Not Sure why the algorithm deleting some of the un-oriented edges