GraphQL\Executor\Executor::getFieldDef PHP Method

    private static function getFieldDef(Schema $schema, ObjectType $parentType, $fieldName)
    {
        static $schemaMetaFieldDef, $typeMetaFieldDef, $typeNameMetaFieldDef;
        $schemaMetaFieldDef = $schemaMetaFieldDef ?: Introspection::schemaMetaFieldDef();
        $typeMetaFieldDef = $typeMetaFieldDef ?: Introspection::typeMetaFieldDef();
        $typeNameMetaFieldDef = $typeNameMetaFieldDef ?: Introspection::typeNameMetaFieldDef();
        if ($fieldName === $schemaMetaFieldDef->name && $schema->getQueryType() === $parentType) {
            return $schemaMetaFieldDef;
        } else {
            if ($fieldName === $typeMetaFieldDef->name && $schema->getQueryType() === $parentType) {
                return $typeMetaFieldDef;
            } else {
                if ($fieldName === $typeNameMetaFieldDef->name) {
                    return $typeNameMetaFieldDef;
                }
            }
        }
        $tmp = $parentType->getFields();
        return isset($tmp[$fieldName]) ? $tmp[$fieldName] : null;
    }