old_contents: from mitmproxy import ctx
  
  
  def load(l):
      ctx.log.info("Registering option 'custom'")
      l.add_option("custom", bool, False, "A custom option")
  
  
  def configure(updated):
      if "custom" in updated:
          ctx.log.info("custom option value: %s" % ctx.options.custom)
  
new_contents: """
  This example shows how addons can register custom options
  that can be configured at startup or during execution
  from the options dialog within mitmproxy.
  
  Example:
  
  $ mitmproxy --set custom=true
  $ mitmproxy --set custom   # shorthand for boolean options
  """
  from mitmproxy import ctx
  
  
  def load(l):
      ctx.log.info("Registering option 'custom'")
      l.add_option("custom", bool, False, "A custom option")
  
  
  def configure(updated):
      if "custom" in updated:
          ctx.log.info("custom option value: %s" % ctx.options.custom)
  
subject: add documentation for custom_option.py