Avoid src_subset and dst_subset in another place within memlet.py.

These subset accesses are entirely symmetric, so no need to know the orientation.

Generally, the library internally should not rely on possibly uninitialized / partially initialized states (or at least explicitly handle such cases).

dace/memlet.py

@@ -561,20 +561,18 @@ def used_symbols(self, all_symbols: bool, edge=None) -> Set[str]:
                 view_edge = True
 
         if not view_edge:
-            if self.src_subset:
-                result |= self.src_subset.free_symbols
-
-            if self.dst_subset:
-                result |= self.dst_subset.free_symbols
+            if self.subset:
+                result |= self.subset.free_symbols
+            if self.other_subset:
+                result |= self.other_subset.free_symbols
         else:
             # View edges do not require the end of the range nor strides
-            if self.src_subset:
-                for rb, _, _ in self.src_subset.ndrange():
+            if self.subset:
+                for rb, _, _ in self.subset.ndrange():
                     if symbolic.issymbolic(rb):
                         result |= set(map(str, rb.free_symbols))
-
-            if self.dst_subset:
-                for rb, _, _ in self.dst_subset.ndrange():
+            if self.other_subset:
+                for rb, _, _ in self.other_subset.ndrange():
                     if symbolic.issymbolic(rb):
                         result |= set(map(str, rb.free_symbols))