Print a warning for the fktables that do not exist during combination

src/pineko/fonll.py

@@ -2,6 +2,7 @@
 
 import copy
 import json
+import logging
 import tempfile
 from pathlib import Path
 
@@ -12,6 +13,8 @@
 
 from . import configs
 
+logger = logging.getLogger(__name__)
+
 
 class FONLLInfo:
     """Class containing all the information for FONLL predictions."""
@@ -44,7 +47,13 @@ def fk_paths(self):
             "ffns5til": self.ffns5til,
             "ffns5bar": self.ffns5bar,
         }
-        return {p: Path(paths[p]) for p in paths if paths[p] is not None}
+        actually_existing_paths = [p for p in paths if paths[p] is not None]
+        for p in paths:
+            if p not in actually_existing_paths:
+                logger.warning(
+                    f"Warning! FK table for {p} does not exist and thus is being skipped."
+                )
+        return {p: Path(paths[p]) for p in actually_existing_paths}
 
     @property
     def fks(self):