docstr: Emit pre-built event
docstr_tok: ["Emit","pre-built","event"]
code: def test_prebuilt_event(self):
      """Emit pre-built event"""
      em = EventEmitter(type="test_event")
      em.default_args["key1"] = "test1"
      em.connect(self.record_event)
  
      self.result = None
      ev = Event(type="my_type")
      em(ev)
      self.assert_result(event=ev, type="my_type")
      assert not hasattr(self.result[0], "key1")
  
imports: import unittest
  import copy
  import functools
  from vispy.util.event import Event, EventEmitter
  from vispy.testing import run_tests_if_main, assert_raises, assert_equal
label_desc: Use image node_id 6 for calling the TestEmitters obj's underlying member method code with example usage: obj.test_prebuilt_event() without return types