Convert py_contains to dot structure

rt/include/python/builtins/list.hpp

@@ -28,9 +28,11 @@ public:
 
   auto append(const T &x) { _v->push_back(x); }
 
-  auto py_contains(const T &x) const {
-    return std::find(_v->begin(), _v->end(), x) != _v->end();
-  }
+  struct : function {
+    template<typename Self> auto operator()(Self self, const T &x) const {
+      return std::find(self.begin(), self.end(), x) != self.end();
+    }
+  } static constexpr py_contains;
 
   auto size() const {
     return _v->size();