code: public static String validateIndexName(@Nullable String indexName) {
      requireNonNull(indexName, "Index name cannot be null");
      checkDbIdentifier(indexName, "Index name", INDEX_NAME_MAX_SIZE);
      return indexName;
    }
docs: Ensure {@code indexName} is a valid name for an index.
  @throws NullPointerException if {@code indexName} is {@code null}
  @throws IllegalArgumentException if {@code indexName} is not valid
  @return the same {@code indexName}
  @see #checkDbIdentifier(String, String, int)