How to run tests from a specific TestSuite instance?

I know how to run specific unittest.TestCases or all cases from a file or folder but how to run all tests from a specific TestSuite instance?

e.g. how to run all tests in "suite" in the following code

from unittest imort TestCase, TestSuite

class TestMain(TestCase):
    def test_true(self):
        self.assert_(True)

suite = TestSuite()
suite.addTest(TestMain('test_inc1'))

Problem is, in run configuration I cannot target the suite instance, just the class i.e. if I pick "test: Class" and choose suite as the value it will (obviously) fail, if I pass TestSuite class it works, but (obviously) finds an empty TestSuite.

As I understand from unittest docs, there is no reason why I should subclass the TestSuite class ... so, am I missing something here? How to run TestCases from a specific TestSuite?

Thank you for input ...

PS Using PyCharm 2.6.2 on Win 7 with Python 2.7.3