human
I wrote the below code

    @custom_model
    def model_a(x, a=1):
        return (x * a)
    class model_b(model_a, ):
        @classmethod
        def evaluate(cls, x, a):
            return (- super(model_b, cls).evaluate(x, a))
    b = model_b()
    assert (b.param_names == (u'a',))
    assert (b.a == 1)
    assert (b(1) == (-1))
    sig = signature(model_b.__init__)
    assert (list(sig.parameters.keys()) == [u'self', u'a', u'kwargs'])
    sig = signature(model_b.__call__)
    assert (list(sig.parameters.keys()) == [u'self', u'x', u'model_set_axis', u'with_bounding_box', u'fill_value', u'equivalencies'])

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

def test_custom_model_subclass():