docstr: KeyError should be raised when accessing non-existing keys.
docstr_tok: ["KeyError","should","be","raised","when","accessing","non-existing","keys","."]
code: def testExceptions(self):
      """KeyError should be raised when accessing non-existing keys."""
      x = event_multiplexer.EventMultiplexer(
          {"run1": "path1", "run2": "path2"}
      )
      with self.assertRaises(KeyError):
          x.Scalars("sv1", "xxx")
  
imports: import os
  import os.path
  import shutil
  import tensorflow
  from tensorboard.backend.event_processing import event_accumulator
  from tensorboard.backend.event_processing import event_multiplexer
label_desc: Use image node_id 9 for calling the EventMultiplexerTest obj's underlying member method code with example usage: obj.testExceptions() without return types