docs: def relation_completions(
      completion_text: str, bel_spec: BELSpec, bel_fmt: str, size: int
  ) -> list:
      """Filter BEL relations by prefix
  
      Args:
          prefix: completion string
          bel_fmt: short, medium, long BEL formats
          spec: BEL specification
  
      Returns:
          list: list of BEL relations that match prefix
      """
  
      if bel_fmt == "short":
          relation_list = bel_spec["relations"]["list_short"]
      else:
          relation_list = bel_spec["relations"]["list_long"]
  
      matches = []
      for r in relation_list:
          if re.match(completion_text, r):
              matches.append(r)
  
      replace_list = []
      for match in matches:
          highlight = match.replace(completion_text, f"<em>{completion_text}</em>")
          replace_list.append(
              {
                  "replacement": match,
                  "label": match,
                  "highlight": highlight,
                  "type": "Relation",
              }
          )
  
      return replace_list[:size]