code: def render(self, namespace):
          '''Render a 'true' or (if available) 'false' block based on a
          boolean.'''
          if (self._isbool and
              namespace[self._evaluate]) or \
              (not self._isbool and
               namespace[self._evaluate](*[namespace[arg]
                                           for arg in self._args])):
              return self._block_true.render(namespace)
          if self._block_false is not None:
              return self._block_false.render(namespace)
          return Nonf render(self, namespace):
          '''Render a 'true' or (if available) 'false' block based on a
          boolean.'''
          if (self._isbool and
              namespace[self._evaluate]) or \
              (not self._isbool and
               namespace[self._evaluate](*[namespace[arg]
                                           for arg in self._args])):
              return self._block_true.render(namespace)
          if self._block_false is not None:
              return self._block_false.render(namespace)
          return None
docs: Render a 'true' or (if available) 'false' block based on a
          boolean.