How to use the phantomas.metadata function in phantomas

minify(
          this.grunt.file.read( TEMPLATE_FILE ),
          {
            removeComments     : true,
            // TODO fix me
            // https://github.com/stefanjudis/grunt-phantomas/issues/93
            collapseWhitespace : true
          }
        ),
        { data : {
          additionalStylesheet : this.options.additionalStylesheet,
          assertions           : this.options.assertions,
          failedAssertions     : this.failedAssertions,
          group                : this.options.group,
          images               : images,
          meta                 : phantomas.metadata.metrics,
          results              : templateResults,
          timestamp            : this.timestamp,
          url                  : this.options.url,
          version              : this.version
        } }
      )
    );

    this.grunt.log.ok(
      'Phantomas created new \'index.html\' at \'' + this.options.indexPath + '\'.'
    );

    resolve( templateResults );

  }.bind( this ) );
};