Allows you to check if a file exists for a locker by passing the file key.
sid (required): A valid session id, received from the "login" method.
partner_token (required): A valid partner token. See Overview for more information.
file_key (required): The file key of the file to check. File keys are n MD5 hash of an uploaded file and are returned in lockerData track results
output (Optional): Your preferred output format. These include xml, and json.
Example Request (searching for artists containing "wave" in the artist name):