'A connection between two nodes.
Its weight indicates the importance (not the cost) of the connection.
Its type is useful in a semantic network (e.g. "is-a", "is-part-of", ...)'

def __init__(self, node1, node2, weight=0.0, length=1.0, type=None, stroke=(0, 0, 0, 1), strokewidth=1):

    self.node1 = node1
    self.node2 = node2
    self._weight = weight
    self.length = length
    self.type = type
    self.stroke = stroke
    self.strokewidth = strokewidth
