code: public int getIsolationLevel() {
          final Optional<IsolationLevel> e = Enums.getIfPresent(IsolationLevel.class, getProperty(ISOLATION_LEVEL).toUpperCase());
  
          if (!e.isPresent()) {
              throw new DatabaseEngineRuntimeException(ISOLATION_LEVEL + " must be set and be one of the following: " + EnumSet.allOf(IsolationLevel.class));
          }
  
          switch (e.get()) {
              case READ_UNCOMMITTED:
                  return Connection.TRANSACTION_READ_UNCOMMITTED;
              case READ_COMMITTED:
                  return Connection.TRANSACTION_READ_COMMITTED;
              case REPEATABLE_READ:
                  return Connection.TRANSACTION_REPEATABLE_READ;
              case SERIALIZABLE:
                  return Connection.TRANSACTION_SERIALIZABLE;
              default:
                  // Never happens.
                  throw new DatabaseEngineRuntimeException("New isolation level?!" + e.get());
          }
      }
docs: Gets the isolation level.
  
  @return The isolation level.