    def test_data_collection_flat_map(self):
        """
        target: test flat_map() API for pipeline
        method: Get the input data, apply it to a function, then output.
        expected: output successfully
        """
        p = towhee.pipe.input('a').flat_map('a', 'b', lambda x: [e+10 for e in x]).output('b')
        res = p([1, 2, 3])
        assert res.get() == [11]
        assert res.get() == [12]
        assert res.get() == [13]

        return True
target: test flat_map() API for pipeline
method: Get the input data, apply it to a function, then output.
expected: output successfully
tests/testcases/test_data_collection.py