Beginner Debug Help : How to trace into $this->file_class(...)

[lowhm]

I am trying to trace the code of SimplePie class which lead me to a line.

 

$file =& new $this->file_class($this->feed_url, $this->timeout, 5, null, $this->useragent, $this->force_fsockopen);

 

I would like to read the code of what is being done inside this file_class call.

 

However, within the class SimplePie, I cannot find any declaration of function file_class.

 

I have search within the whole plugin folder download for wp-o-matic which include the SimplePie class and the only place that has a match is the file itself which contain the above line.

 

Can anyone advice how can I find the actual location of the source of this function call?

 

Thanks.