The CheckMode property is used to indicate whether the condition is expected to exist or not exist in the environment. When ...

The CheckMode property is used to indicate whether the condition is  expected to exist or not exist in the environment.  When the value is True, the condition is expected to exist  (e.g., a file is expected to be on a system) so invoke() is expected to  return True.  When the value is False, the condition is not expect to exist  (e.g., a file is not to be on a system) so invoke is expected to return false