private static boolean isDmgPresent() {
			ResourceFile dmgModule =
				Application.getModuleRootDir(DmgServerProcessManager.DMG_MODULE_NAME);
			if (dmgModule == null) {
				Msg.debug(DmgClientFileSystemFactory.class,
					"The required \"" + DmgServerProcessManager.DMG_MODULE_NAME + "\"" +
						" module is not installed.   You must install this module in order to " +
						"open DMG filesystems.");
				return false;
			}
			return true;
		}
A cached check for the presence of the DMG module.

@return true if the DMG module, is present; otherwise, false.
Ghidra/Features/FileFormats/src/main/java/ghidra/file/formats/ios/dmg/DmgClientFileSystemFactory.java