def get_inner_edges(self):
        """ Returns a list of the internal edges of the tree. """
        inner_edges = [e for e in self._tree.preorder_edge_iter() if e.is_internal()
                       and e.head_node and e.tail_node]
        return inner_edges
def get_inner_edges ( self ) : inner_edges = [ e for e in self . _tree . preorder_edge_iter ( ) if e . is_internal ( ) and e . head_node and e . tail_node ] return inner_edges
Returns a list of the internal edges of the tree.