docs: def get_footnote_backreferences(text, markdown_obj):
      """Retrieves all footnote backreferences within the text.
  
      Fotnote backreferences can be defined anywhere in the text, and
      look like this:
  
          [^id]: text
  
      The corresponding footnote reference can then be placed anywhere in
      the text
  
          This is some text.[^id]
  
      Footnote IDs are case insensitive. Footnote references are also
      removed from the text after they have been retrieved.
  
      RETURNS:
      text       -- str; text with all link labels removed
      references -- dict; link ids to (URL, title), where title is the
                    empty string if it is omitted.
      """
      footnotes = OrderedDict()
      for footnote_id, footnote in re_footnote_backreferences.findall(text):
          footnote_id = re.sub(r'<(.*?)>', r'\1', footnote_id).lower().strip()
          footnote = re.sub(r'^[ ]{0,4}', '', footnote, flags=re.M)
          footnotes[footnote_id] = footnote
      text = re_footnote_backreferences.sub('', text)
      return text, footnotes