code: public function withQualifiedKeyName($keyName)
      {
          $parts = explode('.', $keyName);
  
          if (!isset($parts[1])) {
              throw new \InvalidArgumentException('Expecting a valid qualified column name.');
          }
  
          $this->withIdentifierColumn($parts[1]);
  
          return $this;
      }
docs: Set the column name for the resource's ID.
  
  @param string $keyName
  @return $this
  @todo 2.0 pass qualified key name to the cursor builder.