def it_returns_none_if_no_matching_child_is_present(self, parent_elm):
child_elm = child(parent_elm, 'p:baz')
assert child_elm is None
def it_returns_a_matching_child_if_present(
self, parent_elm, known_child_nsptag_str, known_child_elm):
child_elm = child(parent_elm, known_child_nsptag_str)
assert child_elm is known_child_elm