docs: public VariableNumMap getFirstVariables(int numVariables) {
      int numToCopy = Math.min(numVariables, nums.length);
      int[] newNums = Arrays.copyOf(nums, numToCopy);
      String[] newNames = Arrays.copyOf(names, numToCopy);
      Variable[] newVars = Arrays.copyOf(vars, numToCopy);
      return VariableNumMap.fromSortedArrays(newNums, newNames, newVars);
    }