function parseSchemaDefinition()
{
$start = $this->lexer->token;
$this->expectKeyword('schema');
$directives = $this->parseDirectives();
$operationTypes = $this->many(Token::BRACE_L, [$this, 'parseOperationTypeDefinition'], Token::BRACE_R);
return new SchemaDefinitionNode(['directives' => $directives, 'operationTypes' => $operationTypes, 'loc' => $this->loc($start)]);
}