Extracting file MIME type

This seems simple enough but the answer seems to be eluding me. I want to extract the mime type of a "Moving Image" file attached to an item into a variable for use later in my plugin. My function is passing the $item object and I am testing to verify the $item has a file. But if I do the following:

$fileMime = item_file('mime type', get_current_file());
echo '<p>' . $fileMime . '</p>';

the plugin stops at the point the call is made with no errors. If I change the 'mime type' part to any other valid item like 'size' it still stops at that call. What I am hoping it would do is echo something like

video/x-m4v

Am I calling the wrong function? Am I not passing the right $item object? Other components like $title = item('Dublin Core', 'Title', $item); work fine so am I missing a link somewhere? ANy help would be appreciated.

Even tho this is on the Developers forums I will also post the solution here just in case. The problem was in the case of the item_file call. For MIME types is must be exactly the following:

item_file('MIME Type')

Anything else will result in an error. I originally had this as item_file('mime type') as it was listed int he documentation which is incorrect.

Thanks for posting this here, Greg, and for correcting the documentation!