def __init__(self, edge_type, key, src, tgt):
    self.edge_type = edge_type
    self.id = key
    self.src = src
    self.tgt = tgt
    assert isinstance(src, Node)
    assert isinstance(tgt, Node)
def __init__(self, edge_type, key, src, tgt):
    self.edge_type = edge_type
    self.id = key
    self.src = src
    self.tgt = tgt
    assert isinstance(src, Node)
    assert isinstance(tgt, Node)