Corrected the typing errors linked to a correction for ``black``.

models/analytic_structure.py

@@ -233,7 +233,7 @@
 
         def add_field():
             src = self.format_field_name(slot, prefix, suffix)
-            dest = self.format_field_name(dest_slot, dest_prefix, dest_suffix)
+            dest = self.format_field_name(_dest_slot, dest_prefix, dest_suffix)
             if src in source:
                 try:
                     res[dest] = source[src].id
@@ -246,7 +246,7 @@
         if dest_model is None or dest_model == model:
             for slots in list(src_dim.values()):
                 for slot in slots:
-                    dest_slot = slot
+                    _dest_slot = slot
                     add_field()
 
         else: