demonstrating a problem with the OBS python method signal_handler_disconnect

signal_handler_disconnect_not_working.py

import obspython as obs

obs_signal_handler = obs.obs_get_signal_handler()

# tested in OBS 25.0.6 on OSX. July 26, 2020.

def script_description():
  return """
    Debug signal_handler_disconnect.

    Steps:

      1. open script log.
      2. click 'call add_handlers' button.
      3. observe message in script log: "added 'source_activate' handler."
      4. make a source active.
      5. observe message in script log: "source_activated() called."
      6. click 'call remove_handlers' button.
      7. observe message in script log: "removed 'source_activate' handler."
      8. make a source active.
        * expected: nothing should be printed to the script log
        * actual: "source_activated() called." is printed to the log

    This shows that `obs.signal_handler_disconnect` is not behaving as expected
    or as documented in https://obsproject.com/docs/scripting.html?highlight=disconnect#signal_handler_disconnect
  """

def script_properties():
  props = obs.obs_properties_create()
  obs.obs_properties_add_button(props, "add_button", "call add_handlers", add_handlers)
  obs.obs_properties_add_button(props, "remove_button", "call remove_handlers", remove_handlers)
  return props

# this is the signal handler which will be called.
def source_activated(obs_calldata):
  obs.script_log(obs.LOG_INFO, 'source_activated() called.')

# called when user clicks the 'call add_handlers' button.
#
# it adds a signal handler. whenever a source is activated, the source_activated
# method will be invoked.
def add_handlers(props, prop):
  global obs_signal_handler

  obs.signal_handler_connect(
    obs_signal_handler,
    'source_activate',
    source_activated
  )
  obs.script_log(obs.LOG_INFO, "added 'source_activate' handler.")

# called when user clicks the 'call add_handlers' button.
#
# this should remove the handler added by add_handlers().
# after this is called, no log messages should be written when a source is made
# active. that is not what happens on OBS 25.0.6 on OSX.
def remove_handlers(props, prop):
  global obs_signal_handler

  obs.signal_handler_disconnect(
    obs_signal_handler,
    'source_activate',
    source_activated
  )
  obs.script_log(obs.LOG_INFO, "removed 'source_activate' handler.")

Okay so how to disconnect instead?