    link.connector()

Return a shallow copy of the `connector` property of the link.

For backwards compatibility, if there is no connector, the function also checks whether the legacy `smooth` property is set on the link and returns `{ name: smooth }` if it is.

    link.connector(connector [, opt])

Set the `connector` of the link.

If the `connector` argument is an object, it is expected to have the form `{ name: connectorName, args?: connectorArgs }`. Here `connectorName` is expected to match either the name of a built-in connector or the name of a custom connector.

If the `connector` argument is a function, it is expected to define a custom connector with the signature `function(sourcePoint, targetPoint, vertices, connectorArgs, linkView)` that returns a string representing the SVG path data that will be used to render the link.

    link.connector(connectorName [, connectorArgs, opt])

Set the `connector` of the link to have the value `{ name: connectorName, args: connectorArgs }`.

The `connectorName` string is expected to match either the name of a built-in connector or the name of a custom connector. The `connectorArgs` parameter is optional.