docs: def lowercase_term_id(term_id: str) -> str:
      """Lowercase the term value (not the namespace prefix)
  
      Args:
          term_id (str): term identifier with namespace prefix, e.g. MESH:Atherosclerosis
  
      Returns:
          str: lowercased, e.g. MESH:atherosclerosis
      """
      (ns, val) = term_id.split(":", maxsplit=1)
      term_id = f"{ns}:{val.lower()}"
  
      return term_id