void put_hashset (hashset_ref hash, hashset_key_t key) {
   hashcode_t hashnum = strhash(key) % hash->header_dim;
   if (has_hashset(hashnum, key)== FALSE){
      hashnode_ref newnode = malloc (sizeof (struct hashnode));
      
      char* duped = strdup(key);
      newnode->link = hash->headers;
      hash->headers->link = hash->headers->link->link;
      hash->headers = newnode;
   }
   //printf ("put_hashset (0x%p, %s)", hash, key);
}