human
I wrote the below code

    class TestFilter(Filter, ):
        pass
    def _assert(list, length):
        'Confirm    that    everything    in    the    list    is    a    filter    instance,    and\n                                that    the    list    as    the    required    length.'
        assert (len(list) == length)
        assert bool([f for f in list if isinstance(f, Filter)])
    b = Bundle(filters='jsmin,cssutils')
    _assert(b.filters, 2)
    b = Bundle(filters=['jsmin', 'cssutils'])
    _assert(b.filters, 2)
    assert_raises(ValueError, Bundle, filters=['jsmin,cssutils'])
    b = Bundle(filters=TestFilter)
    _assert(b.filters, 1)
    b = Bundle(filters=[TestFilter, TestFilter, TestFilter])
    _assert(b.filters, 3)
    b = Bundle(filters=TestFilter())
    _assert(b.filters, 1)
    b = Bundle(filters=[TestFilter(), TestFilter(), TestFilter()])
    _assert(b.filters, 3)
    b = Bundle(filters=[TestFilter, TestFilter()])
    _assert(b.filters, 2)
    assert_raises(ValueError, Bundle, filters='notreallyafilter')
    assert_raises(ValueError, Bundle, filters=object())
    Bundle().filters = None
    b = Bundle()
    assert (b.filters is None)
    b.filters = TestFilter
    _assert(b.filters, 1)
    old_filters = b.filters
    b.filters = b.filters
    assert (b.filters == old_filters)

What's a good function header?

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

def test_filter_assign():