code: func IsSlug(text string) bool {
  	if text == "" ||
  		(MaxLength > 0 && len(text) > MaxLength) ||
  		text[0] == '-' || text[0] == '_' ||
  		text[len(text)-1] == '-' || text[len(text)-1] == '_' {
  		return false
  	}
  	for _, c := range text {
  		if (c < 'a' || c > 'z') && c != '-' && c != '_' && (c < '0' || c > '9') {
  			return false
  		}
  	}
  	return true
  }
docs: // IsSlug returns True if provided text does not contain white characters,
  // punctuation, all letters are lower case and only from ASCII range.
  // It could contain `-` and `_` but not at the beginning or end of the text.
  // It should be in range of the MaxLength var if specified.
  // All output from slug.Make(text) should pass this test.