code: @Override
      public String serialize(Collection<String> c, SerializationContext context) {
          StringBuilder sb = new StringBuilder();
          for (String s : c) {
              sb.append(s);
              sb.append(SEPARATOR);
          }
          sb.setLength(sb.length() - SEPARATOR.length());
          return sb.toString();
      }
docs: Serialize a collection of strings separating them with the modifiable TextDeserializer#SEPARATOR string.
  
  @param c        The collection of the object to be serialized
  @param context   Context of the serialization
  
  @return  The serialized string