...F............

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

FAIL: testExpand (tester.ProblemTests)

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Traceback (most recent call last):

  File ".../test.py", line 62, in testExpand

    self.assertEqual(Interval(-3, 10), i.expand(right=-1))

AssertionError: Interval(-3.0, 10.0) != None



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Ran 16 tests in 0.005s



FAILED (failures=1)