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 _calculate_verts(self):
      if self._calculating_verts.is_set():
          return
      self._calculating_verts.set()
      try:
          self._on_calculate_verts()
      finally:
          self._calculating_verts.clear()
      if callable(self.bounds_callback):
          self.bounds_callback()
  
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 18 for calling the PlotModeBase obj's underlying member method code with example usage: obj._calculate_verts() without return types