code: func MergeTmpfsOptions(options []string) ([]string, error) {
  	// We use collisions maps to remove duplicates.
  	// For flag, the key is the flag value (the key for propagation flag is -1)
  	// For data=value, the key is the data
  	flagCollisions := map[int]bool{}
  	dataCollisions := map[string]bool{}
  
  	var newOptions []string
  	// We process in reverse order
  	for i := len(options) - 1; i >= 0; i-- {
  		option := options[i]
  		if option == "defaults" {
  			continue
  		}
  		if f, ok := flags[option]; ok && f.flag != 0 {
  			// There is only one propagation mode
  			key := f.flag
  			if propagationFlags[option] {
  				key = -1
  			}
  			// Check to see if there is collision for flag
  			if !flagCollisions[key] {
  				// We prepend the option and add to collision map
  				newOptions = append([]string{option}, newOptions...)
  				flagCollisions[key] = true
  			}
  			continue
  		}
  		opt := strings.SplitN(option, "=", 2)
  		if len(opt) != 2 || !validFlags[opt[0]] {
  			return nil, fmt.Errorf("Invalid tmpfs option %q", opt)
  		}
  		if !dataCollisions[opt[0]] {
  			// We prepend the option and add to collision map
  			newOptions = append([]string{option}, newOptions...)
  			dataCollisions[opt[0]] = true
  		}
  	}
  
  	return newOptions, nil
  }
docs: // MergeTmpfsOptions merge mount options to make sure there is no duplicate.