code: def _on_navigate(self, event):
      href = event.URL
      if href.startswith("help:"):
          self.__display_help(href[5:])
      elif href.startswith("file:"):
          # Ignore incorrect navigation calls on Mac
          return
      elif href.startswith("loadexample:"):
          self.__load_example_pipeline(href[12:])
          return
      elif href.startswith("pref:"):
          self.__set_startup_blurb()
      elif href.startswith("http"):
          wx.LaunchDefaultBrowser(href)
          # prevent loading in screen
          event.Veto()
  
imports: import glob
  import os.path
  import logging
  import jinja2
  import pkg_resources
  import wx
  import wx.html2
  from cellprofiler_core.preferences import set_startup_blurb
  import cellprofiler.gui.help.content
  import cellprofiler.gui.html
  import cellprofiler.gui.html.utils
  import cellprofiler.gui.utilities.icon
  from cellprofiler.gui.help.content import image_resource_dataUrl
label_desc: Use image node_id 4 for calling the WelcomeFrame obj's underlying member method code with example usage: obj._on_navigate(event) without return types