Returns the edges of the network

        Example
        --------
        >>> from pgmpy.readwrite import BIFReader
        >>> reader = BIFReader("bif_test.bif")
        >>> reader.get_edges()
        [['family-out', 'light-on'],
         ['family-out', 'dog-out'],
         ['bowel-problem', 'dog-out'],
         ['dog-out', 'hear-bark']]

def get_edges(self):
        """
        Returns the edges of the network

        Example
        --------
        >>> from pgmpy.readwrite import BIFReader
        >>> reader = BIFReader("bif_test.bif")
        >>> reader.get_edges()
        [['family-out', 'light-on'],
         ['family-out', 'dog-out'],
         ['bowel-problem', 'dog-out'],
         ['dog-out', 'hear-bark']]
        """
        edges = [[value, key] for key in self.variable_parents.keys()
                 for value in self.variable_parents[key]]
        return edges