public void removeSpriteFramesFromFile(string plist)
{
string path = plist;
string ext = Path.GetExtension (path);
if(ext!=null && ext.Length>0)
path = path.Replace (ext, "");
if(!path.EndsWith("-tp"))
path += "-tp.txt";
NSDictionary dict = NSDictionary.DictionaryWithContentsOfFileFromResources(path);
removeSpriteFramesFromDictionary(dict);
// remove it from the cache
if(_loadedFilenames.Contains(plist))
_loadedFilenames.Remove(plist);
}