code: public static String validateStreamName(String name) {
          Preconditions.checkNotNull(name);
  
          // In addition to user stream names, pravega internally created stream have a special prefix.
          final String matcher = "[" + INTERNAL_NAME_PREFIX + "]?[\\p{Alnum}\\.\\-]+";
          Preconditions.checkArgument(name.matches(matcher), "Name must be " + matcher);
          return name;
      }
docs: Validates an internal stream name.
  
  @param name Stream name to validate.
  @return The name in the case is valid.