code: function (data, id, context) {
              if (!data) {
                  return;
              }
  
              var relativeFilename = FileUtils.getRelativeFilename(this.prefFilePath, context[this.key]);
              if (!relativeFilename) {
                  return;
              }
  
              return _findMatchingGlob(data, relativeFilename);
          }
docs: Gets the location in which the given pref was set, if it was set within
  this path layer for the current path.
  
  @param {Object} data the preference data from the Scope
  @param {string} id preference ID to look up
  @param {Object} context Object with filename that will be compared to the globs
  @return {string} the Layer ID, in this case the glob that matched