text: #include <exception>
  #include <string>
  
  class UnvalidPath : public std::exception
  {
      public :
          UnvalidPath(std::string path)
          {
              message_ = path + " is not a valid path.";
          }
  
          virtual const char* what() const noexcept
          {
              return message_.c_str();
          }
  
      private :
          std::string message_;
  };
  