diff --git a/sphinx/pycode/ast.py b/sphinx/pycode/ast.py
index 3fe0a7fcb..e6f1d2b35 100644
--- a/sphinx/pycode/ast.py
+++ b/sphinx/pycode/ast.py
@@ -81,81 +81,6 @@ class _UnparseVisitor(ast.NodeVisitor):
         else:
             return node.arg
 
-    def visit_Attribute(self, node: ast.Attribute) -> str:
-        return "%s.%s" % (self.visit(node.value), node.attr)
-
-    def visit_BinOp(self, node: ast.BinOp) -> str:
-        return " ".join(self.visit(e) for e in [node.left, node.op, node.right])
-
-    def visit_BoolOp(self, node: ast.BoolOp) -> str:
-        op = " %s " % self.visit(node.op)
-        return op.join(self.visit(e) for e in node.values)
-
-    def visit_Call(self, node: ast.Call) -> str:
-        args = ([self.visit(e) for e in node.args] +
-                ["%s=%s" % (k.arg, self.visit(k.value)) for k in node.keywords])
-        return "%s(%s)" % (self.visit(node.func), ", ".join(args))
-
-    def visit_Dict(self, node: ast.Dict) -> str:
-        keys = (self.visit(k) for k in node.keys)
-        values = (self.visit(v) for v in node.values)
-        items = (k + ": " + v for k, v in zip(keys, values))
-        return "{" + ", ".join(items) + "}"
-
-    def visit_Index(self, node: ast.Index) -> str:
-        return self.visit(node.value)
-
-    def visit_Lambda(self, node: ast.Lambda) -> str:
-        return "lambda %s: ..." % self.visit(node.args)
-
-    def visit_List(self, node: ast.List) -> str:
-        return "[" + ", ".join(self.visit(e) for e in node.elts) + "]"
-
-    def visit_Name(self, node: ast.Name) -> str:
-        return node.id
-
-    if sys.version_info < (3, 8):
-        # these ast nodes were deprecated in python 3.8
-        def visit_Num(self, node: ast.Num) -> str:
-            return repr(node.n)
-
-        def visit_Str(self, node: ast.Str) -> str:
-            return repr(node.s)
-
-        def visit_Bytes(self, node: ast.Bytes) -> str:
-            return repr(node.s)
-
-        def visit_NameConstant(self, node: ast.NameConstant) -> str:
-            return repr(node.value)
-
-        def visit_Ellipsis(self, node: ast.Ellipsis) -> str:
-            return "..."
-
-    def visit_Set(self, node: ast.Set) -> str:
-        return "{" + ", ".join(self.visit(e) for e in node.elts) + "}"
-
-    def visit_Subscript(self, node: ast.Subscript) -> str:
-        return "%s[%s]" % (self.visit(node.value), self.visit(node.slice))
-
-    def visit_UnaryOp(self, node: ast.UnaryOp) -> str:
-        return "%s %s" % (self.visit(node.op), self.visit(node.operand))
-
-    def visit_Tuple(self, node: ast.Tuple) -> str:
-        if node.elts:
-            return ", ".join(self.visit(e) for e in node.elts)
-        else:
-            return "()"
-
-    if sys.version_info >= (3, 6):
-        def visit_Constant(self, node: ast.Constant) -> str:
-            if node.value is Ellipsis:
-                return "..."
-            else:
-                return repr(node.value)
-
-    def generic_visit(self, node):
-        raise NotImplementedError('Unable to parse %s object' % type(node).__name__)
-
     def _visit_arg_with_default(self, arg: ast.arg, default: Optional[ast.AST]) -> str:
         """Unparse a single argument to a string."""
         name = self.visit(arg)
@@ -203,3 +128,78 @@ class _UnparseVisitor(ast.NodeVisitor):
             args.append("**" + self.visit(node.kwarg))
 
         return ", ".join(args)
+
+    def visit_Attribute(self, node: ast.Attribute) -> str:
+        return "%s.%s" % (self.visit(node.value), node.attr)
+
+    def visit_BinOp(self, node: ast.BinOp) -> str:
+        return " ".join(self.visit(e) for e in [node.left, node.op, node.right])
+
+    def visit_BoolOp(self, node: ast.BoolOp) -> str:
+        op = " %s " % self.visit(node.op)
+        return op.join(self.visit(e) for e in node.values)
+
+    def visit_Call(self, node: ast.Call) -> str:
+        args = ([self.visit(e) for e in node.args] +
+                ["%s=%s" % (k.arg, self.visit(k.value)) for k in node.keywords])
+        return "%s(%s)" % (self.visit(node.func), ", ".join(args))
+
+    def visit_Dict(self, node: ast.Dict) -> str:
+        keys = (self.visit(k) for k in node.keys)
+        values = (self.visit(v) for v in node.values)
+        items = (k + ": " + v for k, v in zip(keys, values))
+        return "{" + ", ".join(items) + "}"
+
+    def visit_Index(self, node: ast.Index) -> str:
+        return self.visit(node.value)
+
+    def visit_Lambda(self, node: ast.Lambda) -> str:
+        return "lambda %s: ..." % self.visit(node.args)
+
+    def visit_List(self, node: ast.List) -> str:
+        return "[" + ", ".join(self.visit(e) for e in node.elts) + "]"
+
+    def visit_Name(self, node: ast.Name) -> str:
+        return node.id
+
+    def visit_Set(self, node: ast.Set) -> str:
+        return "{" + ", ".join(self.visit(e) for e in node.elts) + "}"
+
+    def visit_Subscript(self, node: ast.Subscript) -> str:
+        return "%s[%s]" % (self.visit(node.value), self.visit(node.slice))
+
+    def visit_UnaryOp(self, node: ast.UnaryOp) -> str:
+        return "%s %s" % (self.visit(node.op), self.visit(node.operand))
+
+    def visit_Tuple(self, node: ast.Tuple) -> str:
+        if node.elts:
+            return ", ".join(self.visit(e) for e in node.elts)
+        else:
+            return "()"
+
+    if sys.version_info >= (3, 6):
+        def visit_Constant(self, node: ast.Constant) -> str:
+            if node.value is Ellipsis:
+                return "..."
+            else:
+                return repr(node.value)
+
+    if sys.version_info < (3, 8):
+        # these ast nodes were deprecated in python 3.8
+        def visit_Bytes(self, node: ast.Bytes) -> str:
+            return repr(node.s)
+
+        def visit_Ellipsis(self, node: ast.Ellipsis) -> str:
+            return "..."
+
+        def visit_NameConstant(self, node: ast.NameConstant) -> str:
+            return repr(node.value)
+
+        def visit_Num(self, node: ast.Num) -> str:
+            return repr(node.n)
+
+        def visit_Str(self, node: ast.Str) -> str:
+            return repr(node.s)
+
+    def generic_visit(self, node):
+        raise NotImplementedError('Unable to parse %s object' % type(node).__name__)