docstr: Initialize items that were not initialized during addItem().
docstr_tok: ["Initialize","items","that","were","not","initialized","during","addItem","(",")","."]
code: def initializeGL(self):
      """
      Initialize items that were not initialized during addItem().
      """
      ctx = self.context()
      fmt = ctx.format()
      if ctx.isOpenGLES() or fmt.version() < (2, 0):
          verString = glGetString(GL_VERSION)
          raise RuntimeError(
              "pyqtgraph.opengl: Requires >= OpenGL 2.0 (not ES); Found %s"
              % verString
          )
  
      for item in self.items:
          if not item.isInitialized():
              item.initialize()
  
imports: from OpenGL.GL import *
  import OpenGL.GL.framebufferobjects
  from math import cos, radians, sin, tan
  import numpy
  from ..None import Vector
  from ..None import functions
  from ..None import getConfigOption
  from ..Qt import QtCore, QtGui, QtWidgets
label_desc: Use image node_id 8 for calling the GLViewMixin obj's underlying member method code with example usage: obj.initializeGL() without return types