[Graph]: add get_num_edges in edge_list.
[Graph]: add get_num_edges in edge_list.

flashxio/FlashX,icoming/FlashX,flashxio/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashX,flashxio/FlashX,flashxio/FlashX