code: def buildCetExternalSubMenu(self):
      source = "colorcet"
      names = colormap.listMaps(source=source)
      names = [x for x in names if x.startswith("CET")]
      self.buildSubMenu(names, source)
  
imports: import importlib.util
  import re
  import numpy
  from ..None import colormap
  from ..None import functions
  from ..graphicsItems.GradientPresets import Gradients
  from ..Qt import QtCore, QtGui, QtWidgets
label_desc: Use image node_id 5 for calling the ColorMapMenu obj's underlying member method code with example usage: obj.buildCetExternalSubMenu() without return types