code: func (mp *TxPool) isOrphanInPool(hash *chainhash.Hash) bool {
  	if _, exists := mp.orphans[*hash]; exists {
  		return true
  	}
  
  	return false
  }
docs: // isOrphanInPool returns whether or not the passed transaction already exists
  // in the orphan pool.
  //
  // This function MUST be called with the mempool lock held (for reads).