code: def get_prev_sibling_tags(mention):
      
      span = _to_span(mention)
      prev_sibling_tags = []
      i = _get_node(span.sentence)
      while i.getprevious() is not None:
          prev_sibling_tags.insert(0, str(i.getprevious().tag))
          i = i.getprevious()
      return prev_sibling_tags
docs: Return the HTML tag of the Mention's previous siblings.
  
      Previous siblings are Mentions which are at the same level in the HTML tree
      as the given mention, but are declared before the given mention. If a
      candidate is passed in, only the previous siblings of its first Mention are
      considered in the calculation.
  
      :param mention: The Mention to evaluate
      :rtype: list of strings