Update plugins/XmlMaterialProfile/XmlMaterialProfile.py

Co-authored-by: Remco Burema <41987080+rburema@users.noreply.github.com>

plugins/XmlMaterialProfile/XmlMaterialProfile.py

@@ -343,7 +343,7 @@ class XmlMaterialProfile(InstanceContainer):
 
         return stream.getvalue().decode("utf-8")
 
-    def getFileName(self):
+    def getFileName(self) -> str:
         return (self.getMetaDataEntry("base_file") + ".xml.fdm_material").replace(" ", "+")
 
     # Recursively resolve loading inherited files