'Add link to model.'

def addLink(self, source, dest, linktype='data', linkopts=None):

    if (linkopts is None):
        linkopts = {}
    source.links[dest] = self.link
    dest.links[source] = self.link
    self.links[self.link] = {'type': linktype, 'src': source, 'dest': dest, 'linkOpts': linkopts}
