//
        // For example, if the value is unsaved (meaning the user has set it), and
        // it looks like the API resource is persisted with an ID, then we include
        // the object so that parameters are serialized with a reference to its
        // ID.
        //
        // Another example is that on save API calls it's sometimes desirable to
        // update a customer's default source by setting a new card (or other)
        // object with `->source=` and then saving the customer. The
        // `saveWithParent` flag to override the default behavior allows us to
        // handle these exceptions.
        //
        // We throw an error if a property was set explicitly but we can't do
        // anything with it because the integration is probably not working as the
        // user intended it to.
        if (null === $value) {
            return '';
        }
        if (($value instanceof ApiResource) && (!$value->saveWithParent)) {
            if (!$unsaved) {
                return null;
            }
            if (isset($value->id)) {
                return $value;
            }

            throw new Exception\InvalidArgumentException(
                "Cannot save property `{$key}` containing an API resource of type " .
                    \get_class($value) . ". It doesn't appear to be persisted and is " .
                    'not marked as `saveWithParent`.'
            );
        }
        if (\is_array($value)) {
            if (Util\Util::isList($value)) {
                // Sequential array, i.e. a list
                $update = [];
                foreach ($value as $v) {
                    $update[] = $this->serializeParamsValue($v, null, true, $force);
                }
                // This prevents an array that's unchanged from being resent.
                if ($update !== $this->serializeParamsValue($original, null, true, $force, $key)) {
                    return $update;
                }
            } else {
                // Associative array, i.e. a map
                return Util\Util::convertToStripeObject($value, $this->_opts)->serializeParameters();
            }
        } elseif ($value instanceof StripeObject) {
            $update = $value->serializeParameters($force);
            if ($original && $unsaved && $key && static::getAdditiveParams()->includes($key)) {
                $update = \array_merge(self::emptyValues($original), $update);
            }

            return $update;
        } else {
            return $value;
        }
    }

    /**
     * @return mixed
     */
    #[\ReturnTypeWillChange]
    public function jsonSerialize()
    {
        return $this->toArray();
    }

    /**
     * Returns an associative array with the key and values composing the
     * Stripe object.
     *
     * @return array the associative array
     */
    public function toArray()
    {
        $maybeToArray = function ($value) {
            if (null === $value) {
                return null;
            }

            return \is_object($value) && \method_exists($value, 'toArray') ? $value->toArray() : $value;
        };

        return \array_reduce(\array_keys($this->_values), function ($acc, $k) use ($maybeToArray) {
            if ('_' === \substr((string) $k, 0, 1)) {
                return $acc;
            }
            $v = $this->_values[$k];
            if (Util\Util::isList($v)) {
                $acc[$k] = \array_map($maybeToArray, $v);
            } else {
                $acc[$k] = $maybeToArray($v);
            }

            return $acc;
        }, []);
    }

    /**
     * Returns a pretty JSON representation of the Stripe object.
     *
     * @return string the JSON representation of the Stripe object
     */
    public function toJSON()
    {
        return \json_encode($this->toArray(), \JSON_PRETTY_PRINT);
    }

    public function __toString()
    {
        $class = static::class;

        return $class . ' JSON: ' . $this->toJSON();
    }

    /**
     * Sets all keys within the StripeObject as unsaved so that they will be
     * included with an update when `serializeParameters` is called. This
     * method is also recursive, so any StripeObjects contained as values or
     * which are values in a tenant array are also marked as dirty.
     */
    public function dirty()
    {
        $this->_unsavedValues = new Util\Set(\array_keys($this->_values));
        foreach ($this->_values as $k => $v) {
            $this->dirtyValue($v);
        }
    }

    protected function dirtyValue($value)
    {
        if (\is_array($value)) {
            foreach ($value as $v) {
                $this->dirtyValue($v);
            }
        } elseif ($value instanceof StripeObject) {
            $value->dirty();
        }
    }

    /**
     * Produces a deep copy of the given object including support for arrays
     * and StripeObjects.
     *
     * @param mixed $obj
     */
    protected static function deepCopy($obj)
    {
        if (\is_array($obj)) {
            $copy = [];
            foreach ($obj as $k => $v) {
                $copy[$k] = self::deepCopy($v);
            }

            return $copy;
        }
        if ($obj instanceof StripeObject) {
            return $obj::constructFrom(
                self::deepCopy($obj->_values),
                clone $obj->_opts
            );
        }

        return $obj;
    }

    /**
     * Returns a hash of empty values for all the values that are in the given
     * StripeObject.
     *
     * @param mixed $obj
     */
    public static function emptyValues($obj)
    {
        if (\is_array($obj)) {
            $values = $obj;
        } elseif ($obj instanceof StripeObject) {
            $values = $obj->_values;
        } else {
            throw new Exception\InvalidArgumentException(
                'empty_values got unexpected object type: ' . \get_class($obj)
            );
        }

        return \array_fill_keys(\array_keys($values), '');
    }

    /**
     * @return null|ApiResponse The last response from the Stripe API
     */
    public function getLastResponse()
    {
        return $this->_lastResponse;
    }

    /**
     * Sets the last response from the Stripe API.
     *
     * @param ApiResponse $resp
     */
    public function setLastResponse($resp)
    {
        $this->_lastResponse = $resp;
    }

    /**
     * Indicates whether or not the resource has been deleted on the server.
     * Note that some, but not all, resources can indicate whether they have
     * been deleted.
     *
     * @return bool whether the resource is deleted
     */
    public function isDeleted()
    {
        return isset($this->_values['deleted']) ? $this->_values['deleted'] : false;
    }
}