SchemaPrinter.php

<?php 
class SchemaPrinter {
    /**
     * @param Schema $schema
     * @param array  $options
     *
     * @return string
     */
    public static function printFederatedSchema(Schema $schema, array $options = []): string
    {
        $fields = $directives = [];
        $originalQueryType = $schema->getQueryType();
        $federationFields = ['_service', '_entities'];
        $federationDirectives = ['external', 'requires', 'provides', 'key', 'extends'];

        foreach ($originalQueryType->getFields() as $key => $field) {
            if (in_array($key, $federationFields)) {
                continue;
            }

            $fields[] = $field;
        }

        foreach ($schema->getDirectives() as $directive) {
            if (in_array($directive->name, $federationDirectives)) {
                continue;
            }

            $directives[] = $directive;
        }

        $queryType = new ObjectType([
            'name'       => 'Query',
            'fields'     => $fields,
            'interfaces' => $originalQueryType->getInterfaces(),
        ]);

        $newSchema = new Schema([
            'query'        => $queryType,
            'mutation'     => $schema->getMutationType(),
            'subscription' => $schema->getSubscriptionType(),
            'directives'   => $directives,
        ]);

        return self::printFilteredSchema(
            $newSchema,
            static function (Directive $type) {
                return !Directive::isSpecifiedDirective($type);
            },
            static function ($type) {
                return !Type::isBuiltInType($type);
            },
            $options
        );
    }
}