code: function(key, fn) {
      var filepath = this._makeFilepath(key);
  
      fs.exists(filepath, function(exists) {
        if (!exists) {
          return fn();
        }
  
        fs.unlink(filepath, fn);
      });
    }
docs: /*
  @param {Mixed} key - A JSON stringifiable key that is used to lookup
  up a cached file