code: public function setDefaultStrategy($defaultStrategy)
      {
          // for BC
          if (true === $defaultStrategy) {
              @trigger_error('Using "true" as the default strategy is deprecated since version 1.21. Use "html" instead.', E_USER_DEPRECATED);
  
              $defaultStrategy = 'html';
          }
  
          if ('filename' === $defaultStrategy) {
              @trigger_error('Using "filename" as the default strategy is deprecated since version 1.27. Use "name" instead.', E_USER_DEPRECATED);
  
              $defaultStrategy = 'name';
          }
  
          if ('name' === $defaultStrategy) {
              $defaultStrategy = array('Twig_FileExtensionEscapingStrategy', 'guess');
          }
  
          $this->defaultStrategy = $defaultStrategy;
      }
docs: Sets the default strategy to use when not defined by the user.
  
  The strategy can be a valid PHP callback that takes the template
  name as an argument and returns the strategy to use.
  
  @param string|false|callable $defaultStrategy An escaping strategy