@Nullable Object firstParam, ImmutableList<Class<?>> sig) {
    Object[] params = new Object[sig.size()];
    params[0] = firstParam;
    if (params.length > 1) {
      params[1] = "";
      if (params.length > 2) {
        // fill in the rest of the array with arbitrary instances
        for (int i = 2; i < params.length; i++) {
          params[i] = ArbitraryInstances.get(sig.get(i));
        }
      }
    }

      @Nullable Object firstParam, ImmutableList<Class<?>> sig) {
    Object[] params = new Object[sig.size()];
    params[0] = firstParam;
    if (params.length > 1) {
      params[1] = "";
      if (params.length > 2) {
        // fill in the rest of the array with arbitrary instances
        for (int i = 2; i < params.length; i++) {
          params[i] = ArbitraryInstances.get(sig.get(i));
        }
      }
    }