Get a NodeInfo corresponding to a DOM or other external Node, either by wrapping or unwrapping the external Node.
This method is intended for internal use.
@param source A Source representing the wrapped or unwrapped external Node. This will typicallybe a DOMSource, but it may be a similar Source recognized by some other registered external object model.
@return If the Source is a DOMSource and the underlying node is a wrapper around a Saxon NodeInfo,returns the wrapped Saxon NodeInfo. If the Source is a DOMSource and the undelying node is not such a wrapper, returns a new Saxon NodeInfo that wraps the DOM Node. If the Source is any other kind of source, it is offered to each registered external object model for similar treatment. The result is the NodeInfo object obtained by wrapping or unwrapping the supplied external node.
@throws IllegalArgumentException if the source object is not of a recognized class. This method does
not call the registered {@link SourceResolver to resolve the Source}.