Add forwarding constructors to PyDict and PyStr

rt/include/python/builtins/dict.hpp

@@ -89,10 +89,12 @@ public:
   PyDict(std::unordered_map<K, V> &&m)
       : _m(std::move(
             std::make_shared<std::unordered_map<K, V>>(std::move(m)))) {}
-  PyDict(std::initializer_list<std::pair<K, V>> &&m)
+  PyDict(std::initializer_list<std::pair<const K, V>> &&m)
       : _m(std::make_shared<std::unordered_map<K, V>>(std::move(m))) {}
 
   PyDict() : _m(std::make_shared<std::unordered_map<K, V>>()) {}
+  template<typename... Args>
+  PyDict(Args&&... args) : _m(std::make_shared<std::unordered_map<K, V>>(std::forward<Args>(args)...)) {}
 
   auto begin() const { return _m->begin(); }
   auto end() const { return _m->end(); }

rt/include/python/builtins/str.hpp

@@ -18,11 +18,11 @@ using namespace std::literals;
 class PyStr : public std::string {
 public:
   PyStr() : std::string() {}
-  PyStr(const char *s) : std::string(s) {}
   PyStr(const std::string &s) : std::string(s) {}
   PyStr(std::string &&s) : std::string(std::move(s)) {}
-  PyStr(size_t count, char ch) : std::string(count, ch) {}
   constexpr PyStr(const char *s, size_t count) : std::string(s, count) {}
+  template<typename... Args>
+  PyStr(Args&&... args) : std::string(std::forward<Args>(args)...) {}
 
   template <class InputIterator>
   PyStr(InputIterator first, InputIterator last) : std::string(first, last) {}