code: function(actual, expected, negate, name) {
        return 'expected ' + puts(actual) + ' to ' + 
                 (negate ? 'not ' : '') + 
                    name.replace(/_/g, ' ') +
                      ' ' + (expected.length > 1 ?
                        puts.apply(this, expected.slice(1)) :
                          '')
      }
docs: Default matcher message callback.
  
  @api private