system/classes/Collection.php
public function __isset($name)
    {
      $value = $this->find($name);
      if ($value !== null && !($value instanceof \Exception)) {
          return true;
      }
      return false;
    }
public function __isset($name)
    {
      $value = $this->find($name);
      if ($value !== null && !($value instanceof \Exception)) {
          return true;
      }
      return false;
    }
Determines if a resource exists.

@param name The name of the resource sought.
@return Boolean