code: public function validateOperationParams(OperationParams $params)
      {
          $errors = [];
          if (! $params->query && ! $params->queryId) {
              $errors[] = new RequestError('GraphQL Request must include at least one of those two parameters: "query" or "queryId"');
          }
  
          if ($params->query && $params->queryId) {
              $errors[] = new RequestError('GraphQL Request parameters "query" and "queryId" are mutually exclusive');
          }
  
          if ($params->query !== null && (! is_string($params->query) || empty($params->query))) {
              $errors[] = new RequestError(
                  'GraphQL Request parameter "query" must be string, but got ' .
                  Utils::printSafeJson($params->query)
              );
          }
  
          if ($params->queryId !== null && (! is_string($params->queryId) || empty($params->queryId))) {
              $errors[] = new RequestError(
                  'GraphQL Request parameter "queryId" must be string, but got ' .
                  Utils::printSafeJson($params->queryId)
              );
          }
  
          if ($params->operation !== null && (! is_string($params->operation) || empty($params->operation))) {
              $errors[] = new RequestError(
                  'GraphQL Request parameter "operation" must be string, but got ' .
                  Utils::printSafeJson($params->operation)
              );
          }
  
          if ($params->variables !== null && (! is_array($params->variables) || isset($params->variables[0]))) {
              $errors[] = new RequestError(
                  'GraphQL Request parameter "variables" must be object or JSON string parsed to object, but got ' .
                  Utils::printSafeJson($params->getOriginalInput('variables'))
              );
          }
  
          return $errors;
      }
docs: Checks validity of OperationParams extracted from HTTP request and returns an array of errors
  if params are invalid (or empty array when params are valid)
  
  @return Error[]
  
  @api