naming convention for files used for imds and pxds in pixelLabelImageSource

I am using pixelLabelImageSource to create a datasource for semantic segmentation. It is not clear to me, after reading documentation, if there needs to be a naming convention for the image files that are the source of labels, as they relate to their associated images that are used for imds. Can anyone provide clarification? The computer vision toolbox data has one set of examples with "image_x.jpg" for the images and "labeled_image_x.png" for the associated label image. But another example involves "buildingx.jpg" and "Label_x.png".