code: public static void validateSimpleKeys(String... keys) {
          for (String key : keys) {
              if (!key.isEmpty() && key.startsWith(NAMESPACE)) {
                  throw CompositeKeyFormatException.forSimpleKey(key);
              }
          }
      }
docs: To ensure that simple keys do not go into composite key namespace,
  we validate simple key to check whether the key starts with 0x00 (which
  is the namespace for compositeKey). This helps in avoding simple/composite
  key collisions.
  
  @throws CompositeKeyFormatException if First character of the key