message: Add error if num_chains is supplied to non-HMC algorithm
diff: @@ -361,6 +361,10 @@ int command(int argc, const char *argv[]) {
  "num_chains can currently only be used for NUTS with adaptation "
  "and dense_e or diag_e metric");
  }
  + } else {
  + throw std::invalid_argument(
  + "num_chains can currently only be used for HMC with adaptation "
  + "engaged");
  }
  }
  }
  