* context, either {@link Vertex#TYPE_INPUT_PORT},
* {@link Vertex#TYPE_OUTPUT_PORT} or {@link Vertex#TYPE_PORT}.
* @return A port name if found, <code>null</code> otherwise.
*/
private String getPort(Vertex vertex, String edgePort, String[] portTypes) {
IRefinementPolicy policy = vertex.getConfiguration()
.getRefinementPolicy();
IFile sourceFile = policy.getRefinementFile(vertex);
// open the refinement
if (sourceFile != null) {
List<String> ports = getPorts(sourceFile, portTypes);
if (!ports.isEmpty()) {