class_docstr: Intended parent class for plotting
  modes. Provides base functionality
  in conjunction with its parent,
  PlotMode.
class_docstr_tok: ["Intended","parent","class","for","plotting","modes",".","Provides","base","functionality","in","conjunction","with","its","parent",",","PlotMode","."]
code: def _render_stack_top(self, render_stack):
      top = render_stack[-1]
      if top == -1:
          return -1  # nothing to display
      elif callable(top):
          dl = self._create_display_list(top)
          render_stack[-1] = (dl, top)
          return dl  # display newly added list
      elif len(top) == 2:
          if pgl.GL_TRUE == pgl.glIsList(top[0]):
              return top[0]  # display stored list
          dl = self._create_display_list(top[1])
          render_stack[-1] = (dl, top[1])
          return dl
  
imports: import pyglet.gl
  from sympy.core import S
  from sympy.plotting.pygletplot.color_scheme import ColorScheme
  from sympy.plotting.pygletplot.plot_mode import PlotMode
  from sympy.utilities.iterables import is_sequence
  from time import sleep
  from threading import Thread, Event, RLock
  import warnings
label_desc: Use image node_id 11 for calling the PlotModeBase obj's underlying member method code with example usage: obj._render_stack_top(render_stack) and returns: unknown, dl, dl, top