Add some useful functions to PyStr

rt/include/python/builtins/str.hpp

@@ -12,7 +12,7 @@ using namespace std::literals;
 
 #include "bytes.hpp"
 #include "print.hpp"
-//#include <format>
+// #include <format>
 #include <fmt/format.h>
 
 class PyStr : public std::string {
@@ -22,6 +22,7 @@ public:
   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 <class InputIterator>
   PyStr(InputIterator first, InputIterator last) : std::string(first, last) {}
@@ -33,6 +34,8 @@ public:
   template <typename... T> PyStr format(T &&...args) const {
     return PyStr(fmt::format(fmt::runtime(*this), std::forward<T>(args)...));
   }
+
+  bool startswith(const std::string &s) const { return this->starts_with(s); }
 };
 
 inline constexpr PyStr operator""_ps(const char *s, size_t len) noexcept {