public function removeTransactionMethod($method)
    {
        // if it's not an array, there are no transaction methods
        if (!is_array($this->transactionMethods)) {
            return $this;
        }
        
        // find method in transactionMethods
        $index = array_search($method, $this->transactionMethods);
        
        // remove the method if it exists in array
        if ($index !== false) {
            array_splice($this->transactionMethods, $index, 1);
        }


        // if transaction methods are empty set them to null
        if (empty($this->transactionMethods)) {
            $this->transactionMethods = null;
        }

        return $this;
    }