...........E....

======================================================================

ERROR: testOpen (tester.ProblemTests)

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Traceback (most recent call last):

  File ".../test.py", line 49, in testOpen

    self.assertFalse(i.open())

AttributeError: Interval instance has no attribute 'open'



----------------------------------------------------------------------

Ran 16 tests in 0.009s



FAILED (errors=1)