code: function sameParentChecker (preprocessFn) {
      return function (suggestions) {
          if (suggestions.length === 0) {
              return false;
          }
          if (suggestions.length === 1) {
              return true;
          }
  
          var parentValue = preprocessFn(suggestions[0].value),
              aliens = suggestions.filter(function (suggestion) {
                  return preprocessFn(suggestion.value).indexOf(parentValue) !== 0;
              });
  
          return aliens.length === 0;
      }
  }
docs: Factory to create same parent checker function
  @param preprocessFn called on each value before comparison
  @returns {Function} same parent checker function