docstr: The EmitterGroup basic construction
docstr_tok: ["The","EmitterGroup","basic","construction"]
code: def test_group_construction(self):
      """The EmitterGroup basic construction"""
      grp = EmitterGroup(em1=Event, em2=BasicEvent, em3=TypedEvent)
  
      grp.em1.connect(self.record_event)
      grp.em2.connect(self.record_event)
      grp.em3.connect(self.record_event)
      self.result = None
      ev = grp.em1()
      self.assert_result(event=ev, type="em1", event_class=Event)
      ev = grp.em2()
      self.assert_result(event=ev, type="em2", event_class=BasicEvent)
      ev = grp.em3()
      self.assert_result(
          event=ev, type="typed_event", event_class=TypedEvent
      )
  
imports: import unittest
  import copy
  from vispy.util.event import Event, EventEmitter, EmitterGroup
  from vispy.util import use_log_level
  from vispy.testing import run_tests_if_main, assert_true, assert_raises
label_desc: Use image node_id 1 for calling the TestGroups obj's underlying member method code with example usage: obj.test_group_construction() without return types