docs: async def delete_cas(self, key, *, index):
          """Deletes the Key with check-and-set semantics.
  
          Parameters:
              key (str): Key to delete
              index (ObjectIndex): Index ID
          Response:
              bool: ``True`` on success
  
          The Key will only be deleted if its current modify index matches the
          supplied Index.
          """
          index = extract_attr(index, keys=["ModifyIndex", "Index"])
          response = await self._discard(key, cas=index)
          return response.body is True