code: public function parseLiteral(/* GraphQL\Language\AST\ValueNode */
          $valueNode,
          ?array $variables = null
      ) {
          if (isset($this->config['parseLiteral'])) {
              return call_user_func($this->config['parseLiteral'], $valueNode, $variables);
          }
  
          return AST::valueFromASTUntyped($valueNode, $variables);
      }
docs: @param Node         $valueNode
  @param mixed[]|null $variables
  
  @return mixed
  
  @throws Exception