diff --git a/qlat/auto_contractor/compile.py b/qlat/auto_contractor/compile.py
index 4d912814..f88476f1 100644
--- a/qlat/auto_contractor/compile.py
+++ b/qlat/auto_contractor/compile.py
@@ -791,6 +791,20 @@ def collect_op(self):
         # collect common prod into variables
         self.variables_prod = collect_subexpr_in_cexpr(self.variables_tr)
 
+    def list(self):
+        return [
+                self.diagram_types,
+                self.positions,
+                self.variables_factor_intermediate,
+                self.variables_factor,
+                self.variables_prop,
+                self.variables_color_matrix,
+                self.variables_prod,
+                self.variables_tr,
+                self.named_terms,
+                self.named_exprs,
+                ]
+
 ### ----
 
 def increase_type_dict_count(type_dict, key):
diff --git a/qlat/auto_contractor/wick.py b/qlat/auto_contractor/wick.py
index 1739db07..67fa2067 100644
--- a/qlat/auto_contractor/wick.py
+++ b/qlat/auto_contractor/wick.py
@@ -109,7 +109,7 @@ def __repr__(self) -> str:
             return f"{self.otype}({self.f!r},{self.p!r},{self.s!r},{self.c!r})"
 
     def list(self):
-        return [self.otype, self.f, self.p, self.s, self.c]
+        return [ self.otype, self.f, self.p, self.s, self.c, ]
 
     def __eq__(self, other) -> bool:
         return self.list() == other.list()
@@ -203,7 +203,7 @@ def __repr__(self) -> str:
             return f"{self.otype}({self.f!r},{self.p1!r},{self.p2!r},{self.s1!r},{self.s2!r},{self.c1!r},{self.c2!r})"
 
     def list(self):
-        return [self.otype, self.f, self.p1, self.p2, self.s1, self.s2, self.c1, self.c2]
+        return [ self.otype, self.f, self.p1, self.p2, self.s1, self.s2, self.c1, self.c2, ]
 
     def __eq__(self, other) -> bool:
         return self.list() == other.list()
@@ -246,7 +246,7 @@ def __repr__(self) -> str:
             return f"{self.otype}({self.tag!r},{self.s1!r},{self.s2!r})"
 
     def list(self):
-        return [self.otype, self.tag, self.s1, self.s2]
+        return [ self.otype, self.tag, self.s1, self.s2, ]
 
     def __eq__(self, other) -> bool:
         return self.list() == other.list()
@@ -280,7 +280,7 @@ def __repr__(self) -> str:
             return f"{self.otype}({self.tag!r},{self.p!r},{self.mu!r},{self.c1!r},{self.c2!r})"
 
     def list(self):
-        return [self.otype, self.tag, self.p, self.mu, self.c1, self.c2]
+        return [ self.otype, self.tag, self.p, self.mu, self.c1, self.c2, ]
 
     def __eq__(self, other) -> bool:
         return self.list() == other.list()
@@ -340,7 +340,7 @@ def __repr__(self) -> str:
         return f"{self.otype}({self.ops!r},{self.tag!r})"
 
     def list(self):
-        return [self.otype, self.tag, self.ops]
+        return [ self.otype, self.tag, self.ops, ]
 
     def __eq__(self, other) -> bool:
         return self.list() == other.list()