code: def push(self, x):
          
          if isinstance(x, Frame):
              frame = x
          else:
              frame = Frame(x)
          self.stack.append(frame)
          log.debug('push: (%s)\n%s', Repr(frame), Repr(self.stack))
          return frame
docs: Push an I{object} onto the stack.
          @param x: An object to push.
          @type x: L{Frame}
          @return: The pushed frame.
          @rtype: L{Frame}