'Return a list of all subsection titles on the page
for the section at index `section_index` (starts at 1).'

def _subsection_titles(self, section_index):

    subsection_css = self.SUBSECTION_TITLES_SELECTOR.format(section_index)
    return self.q(css=subsection_css).map((lambda el: el.get_attribute('innerHTML').strip())).results
