code: public static SimpleIndexMainType parseMainType(String s) {
      List<String> split = SEPARATOR_SPLITTER.splitToList(s);
      checkArgument(split.size() >= 2, "Unsupported IndexType value: %s", s);
  
      return new SimpleIndexMainType(split.get(0), split.get(1));
    }
docs: Parse a String generated by {@link #format()} to extract the simple details of the main type.
  <p>
  Note: neither {@link IndexMainType} nor {@link IndexRelationType} can be parsed from the string generated by
  {@link #format()} as the generated string does not contain the {@link Index#acceptsRelations() acceptsRelations}
  flag).