code: def contrib_xref(contrib_tag, ref_type):
      
      aff_tags = []
      for child_tag in contrib_tag:
          if (child_tag and child_tag.name and child_tag.name == "xref"
              and child_tag.get('ref-type') and child_tag.get('ref-type') == ref_type):
              aff_tags.append(child_tag)
      return aff_tags
docs: Given a contrib tag, look for an xref tag of type ref_type directly inside the contrib tag