    def test_data_collection_output_schema(self):
        """
        target: test output() API for pipeline
        method: Close and preload an existing pipeline
        expected: output successfully
        """
        p = towhee.pipe.input('a').map('a', 'b', lambda x: x+1).output('b')
        assert p(100).get() == [101]

        # Output empty
        q = towhee.pipe.input('a').map('a', 'b', lambda x: x + 1).output()
        assert q(10).get() == None

        return True
target: test output() API for pipeline
method: Close and preload an existing pipeline
expected: output successfully
tests/testcases/test_data_collection.py