human
I wrote the below code

    def mock_kpsewhich(filename):
        nt.assert_equal(filename, 'breqn.sty')
        return None
    for (s, wrap) in [('$x^2$', False), ('x^2', True)]:
        (yield (latextools.latex_to_png_mpl, s, wrap))
        with patch.object(latextools, 'kpsewhich', mock_kpsewhich):
            (yield (latextools.latex_to_png_mpl, s, wrap))

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

@skipif_not_matplotlib
def test_latex_to_png_mpl_runs():