human
I wrote the below code

    a = testdir.mkdir('a')
    fh = a.join('test_a.py')
    fh.write(_pytest._code.Source('\n                                import    pytest\n                                def    test_real():\n                                                pass\n                '))
    result = testdir.runpytest('--keep-duplicates', a.strpath, a.strpath)
    result.stdout.fnmatch_lines(['*collected    2    item*'])

What's a good function header?
 ... Here's a good function header?
assistant
#Here's a good function header.

def test_keep_duplicates(testdir):