def __repr__(self):
        return "<Requirement(package={package}, version='{version}')>".format(
            package=self.package, version=self.version)
def setTail(self, pt):
        self.pt = pt
        self.Tail.Eq(pt)
        self.Head.setPoint(self.pt.x + self.x, self.pt.y + self.y)