Given a dictionary mapping each feature to the pathways
        overrepresented in the feature, build a CoNetwork by
        creating edges for every pairwise combination of pathways in a feature.

def _edges_from_permutation(self, feature_pathway_dict):
        """Given a dictionary mapping each feature to the pathways
        overrepresented in the feature, build a CoNetwork by
        creating edges for every pairwise combination of pathways in a feature.
        """
        network_edges = {}
        for feature, pathway_list in feature_pathway_dict.items():
            for i in range(len(pathway_list)):
                for j in range(i + 1, len(pathway_list)):
                    vertex_i = pathway_list[i]
                    vertex_j = pathway_list[j]
                    new_edge = self.edge_tuple(vertex_i, vertex_j)
                    if new_edge not in network_edges:
                        network_edges[new_edge] = []
                    network_edges[new_edge].append(feature)
        self._augment_network(network_edges)