def merge_edges(cls, e1: Edge, e2: Edge) -> Edge:
"merge two edges if they have the same id"
e1id = e1.id()
e2id = e2.id()
if e1id() != e2id():
msg = "Can not merge edges with different ids: "
msg += "first edge id: " + e1id
msg += "second edge id: " + e2id
raise ValueError(msg)
#
e1data = e1.data()
e2data = e2.data()
e1data.update(e2data)
e1info = e1.info()
e2info = e2.info()
#
einfo = NodeInfo()
einfo.set_to_null(e1info.first())
einfo.set_to_null(e1info.second())
einfo.set_to_null(e2info.first())
einfo.set_to_null(e2info.second())
return Edge(edge_id=e1id,
edge_type=e1.type(),
data=ei1data,
node_info=einfo)
