docs: def removeUnreferencedIDs(referencedIDs, identifiedElements):
      """
      Removes the unreferenced ID attributes.
  
      Returns the number of ID attributes removed
      """
      global _num_ids_removed
      keepTags = ['font']
      num = 0
      for id in identifiedElements:
          node = identifiedElements[id]
          if id not in referencedIDs and node.nodeName not in keepTags:
              node.removeAttribute('id')
              _num_ids_removed += 1
              num += 1
      return num